Rhaegar's Catspaw Assassin

The iron tones are a good catch. Especially since Rhaegar is so often described as sad.

As for

But in his dream under the rock, Jaime sees Rhaegar as the "rightful heir." And says he left his children in Jaime's hands. In this scene, the last time he spoke to Rhaegar, Rhaegar doesn't put the children in Jaime's charge. Only seems to put Jaime in charge of "crutching" (I'm going to pretend that's a verb) Aerys. Of keeping him steady.

So, if Jaime in Storm sees Rhaegar as rightful heir to the Iron Throne, with his Iron-toned voice--Jaime may not fear the "mosaic" dragon. The dragon as a combination or symbol. But Rhaegar. . . that one he respects.


Is this innately a contradiction? I think I see what you are getting at, though I'm not sure we've seen signs of Darry as sarcastic before this.

But I thought Jaime is supposed to guard the king. And therefore obey Rhaegar who tells him to stay. Not argue with Rhaegar. I'd read this as Darry swatting down Jaime's complaint as cheek.



Not sure I'd go as far as "sperm donor," but he does seem willing to break from his father. And, in this same book, we see Jaime's willingness to break from Cersei. And in Storm, from Cersei and Tywin (Jaime even thinks that he has no father when he sends Brienne to protect Sansa).

Though I agree on the changes--also echoes Jaime in the same book--when he's in the Riverlands contemplating changes to the ruling in Kings Landing for the sake of his son. But is that so much "sinister" as "practical?" Though I don't suppose the two are innately contradictory.

Will be back to finish when I have more time and can dig into the rest and sfdanny's arguments.

Overall--I like the potential for this--but not sold on this being a set up. . . unless you are arguing Jaime didn't know he was being set up as catspaw?

Thank you It is an incredibly interesting exchange, isn't it? Jaime is no slouch in battle. He is one of the best swordsmen in the series, and was nearly at Rhaegar's side at the Battle of the Trident. The mere fact that Jaime longed to be there with Rhaegar is interesting to me, and seems to contradict the idea that Jaime (and perhaps by extension, House Lannister) ever shared common cause with the rebel forces.

Dany has been taught about the Usurper's Dogs, and includes the Lion in that kennel. But I think that's wrong. Jaime was indeed loyal to a usurper, but it wasn't Robert.

I had not considered the rape angle at all, to be honest. I was merely stricken by Rhaegar's word choice for his "royal sire." It's completely detached. Even Prince Joffrey showed more affection and respect for his father.

So, I can only agree. If Rhaegar knew of the rape I think it makes the case even stronger for his desire to kill his father. And really, how could Rhaegar not have known? Unless Aerys only committed the single rape Jaime remembered, and Rhaegar never noticed his father's nature growing up... seems unlikely.

The pyromancer plot is debatable, but Jaime knew of it. Jaime isn't as gullible as Ned, but he isn't exactly a great detective. If he knew, the other kingsguard knights likely knew. And we know that some of the kingsguard appear to be quite loyal to Rhaegar.

Let's examine the Great Council precedent in a bit more detail...


Only the Great Council of 101 AC was held whilst the King lived, and that Great Council was called by the King himself. As it happens, it was called in order to determine the Old King's heir, because there were simply too many. He assembled the lords and they chose Viserys I. His tenure of course led to the Dance.

So I would argue that one thing that all of the Great Councils have in common is a dead king. Even the one Jaehaerys himself organized was to make the heir clear in the event of his death...which came only two years later.

The glaring contingent of a Great Council is the death of the king. There are no impeachments in a monarchy. As Cersei pointed out, "When you play the game of thrones, you win or you die. There is no middle ground."

Unless Rhaegar assumed Aerys would willingly abdicate the throne (a proposition that I think you would agree is unlikely), Rhaegar's road not taken had to include the death of his royal sire.

Jaime knows this.

We agree, but I think we likely see Rhaegar's act of hiding away differently.

This seems very strange, doesn't it? Why would Rhaegar let his wife and children return to KL? Why wouldn't he be with them?

Why would Rhaegar be in hiding anyway as his beloved realm turned from tinderbox to inferno?

I think he planned to kill Aerys long ago, but chickened out. He then expected victory at the Trident, and he expected to be able to call a Great Council after the battle. That means Aerys must needs die in the interim.

I agree. But I can't help but wonder if Rhaegar was willing to pay such prices. Would Ned have gone into hiding while Cersei had designs upon his family? Would Ned have rode off to battle leaving them in the Red Keep as hostages? We can't know of course, but I don't think he would have.

Either Rhaegar intentionally left his wife and children in harm's way, or he knew the Lions would protect them. I'm leaning toward the latter.

It is no mistake that Lannister claws found them.

A Storm of Swords - Tyrion VI
Considering this, who would have protected Rhaegar's children from "Ned Stark's van" had Robert fallen to Rhaegar at the Trident?

I argue Tywin was ready to do just that, and from his concerns above it also sounds as if he knew Jaime could kill Aerys.

Either Rhaegar vastly underestimated his royal sire's "crutch" while many leagues away Tywin had his son's accurate measure, or Rhaegar knew his men. His Kingsguard in all but name...

This part of Tywin's confession is particularly convincing to me: We had come late to Robert's cause. It was necessary to demonstrate our loyalty. When I laid those bodies before the throne, no man could doubt that we had forsaken House Targaryen forever.

Did the Lion not demonstrate its loyalty by killing the Mad King? It seems Tywin is convinced that was not an act done to secure Robert's favor, and that a further gesture was required.

If the Lion's men had not laid those bodies before the throne, and instead ushered Queen Elia and her children to her victorious husband, no man could doubt they had remained loyal to House Targaryen forever.

And do you think Aerys would allow himself to be removed? The pots of wildfire around Kings Landing seem to suggest otherwise. If Rhaegar had even a suspicion that Aerys would do something mad, rather than willingly step down, I think it is highly likely he had a plan in place to ensure there was a Throne left to claim after the Battle of the Trident.

Just imagine how much luck we have to assume he would have had otherwise. He would have returned victorious, his wife and children protected from not only Aerys, but Ned Stark's van... And... on top of this, rather than roast the city alive, his royal sire has conveniently been dispatched by a young knight who was literally begging him to tag along for the fight.

It's a lot to accept as mere happenstance.

Sounds very interesting.

Keep? I think Jaime's loyalty is spilling out all over the place. Jaime has broken decorum, and earns a reprimand from Darry. Rhaegar knows Jaime is his, a Kingsguard Knight, and that he is not Aerys' crutch.

And call me crazy, but I don't think Jaime was ignorant of his status in Aerys' eyes, nor do I think he had any intention nor fear of being a hostage. Not only did Jaime know he could kill the king, he knew he could get by with doing it and keeping the Iron Throne warm for Rhaegar's return...after all, it spoke to him:



Possible. After all, we have no reason to think Rhaegar held his mother in ill regard.

I think it is interesting that Rhaegar trusts Jaime to protect his family, while Tywin simultaneously suspects Jaime could do something to Aerys. Unless Rhaegar was a bit daft, I think he'd suspect that too.

It is. Thus we know Rhaegar trusted Jaime to be his sworn sword, not his royal sire's.

After all, he wouldn't need an exit for his wife and children if he'd already left his royal sire with a murderous crutch yearning to please his Prince.

Keep? I ask again... I don't think Rhaegar fears treachery from Jaime. If anything, this passage demonstrates that he trusts Jaime with all he holds dear, and knows his royal sire can harm them not whilst he has his crutch.

Many thanks sfdanny . I'm looking forward to more. :::

Indeed. I think it also shows that Rhaegar trusted Jaime in a way no one else ever has - before or since.

Everyone of the rebels, yes. Ned had his suspicions - which is saying something! LOL

I think Rhaegar knew the Lions were his.

And unless Rhaegar had the wit the gods gave a goose, I think he knew the Lions wanted Aerys to die as much as he needed for him to die. Common interests.

Problem I have with this is that it seems almost like it's in code. Like Jaime doesn't get it (his scene with Brienne). Like trying to read the 3KG at the tower as defending someone in the tower--only there, we have the wiggle room of a dream leaving out key info.

Here, Jaime's giving us the memory straight. Are you assuming Jaime knew Rhaegar was asking for this? And, if so, why not include it in the confession to Brienne?


Perhaps--though the sworn duty is to guard/stand by the king. Not always to go into battle.

True--but is Rhaegar calling the shots re: who goes and who stays? If so, why in the name of all that's holy would he leave Elia and the children if he knows about the wildfire plot? That's madness!

Good point. Though Rhaegar has given himself deniability with vagueness in the scene. And they would be risking their own lives marching Rhaegar into Aerys' presence with such a tale.


We only get this scene. But yes, fair point. And it does remind me of Jaime's thoughts re: Tywin when he sends Brienne. Which is also a kind of treason. And protecting the one he thinks killed Joff. Because, as he thinks, "Joffrey deserved it."

So, that echo might work in your theory's favor.


Errmmm not always. When he's reading the White Book before the first Kingsguard Orientation Meeting, he thinks Arthur Dayne would wonder why the KG have fallen so low. And thinks that he, Jaime, would have to tell Dayne that it's Jaime's fault. He allowed all of this lack of honor in. Thinks of his own failures.

And as for killing the king--there's a difference between sarcastic defiance and holding one's head high, no?

Agreed re: Jaime's loyalty--he feels a lot of guilt re: failing Rhaegar. His feelings re: Aerys are messy. Towards Rhaegar is just pure pain.

And I agree that death would be the easiest way out. Just as Robert knew this re: Rhaegar's children. But. . .after this war, the Council might have gotten it done. . .


Really? Rhaegar would have been the hero. The one on the field (or in the river). Knighting men after the fight. Riding on King's Landing, triumphant. It's a risk, yes. But that win might have put Rhaegar over the top.

But in defense of your theory, one way or another, he kept Hightower out of the fight. But he also kept Arthur and Whent out, too. Which makes me wonder A. what was their "post battle" role? And B: did he leave them behind in part to keep them from being hurt by Aerys?



Trusting a kid to snap and stab? That's one hell of a risk to take with his wife and children. . .


If Rhaegar knew Tywin's mind, perhaps. But, again, expecting/hoping Jaime would do this. . . without telling him to do it. . . seems like a HUGE risk for book boy.


"Happily" worked for the Throne under Rhaegar? Sure. "Loyal?" That's a whole other kettle of fish.


True.

But Tywin was putting a lot of faith in his kid's snapping. It's not like his putting faith in Tyrion's ruling abilities.

Okay....long post alarum!

That's precisely why I have drawn this conclusion. Jaime wants to go with Rhaegar. And where is Rhaegar going?

Jaime doesn't want to be a crutch, he wants to kill for his king. Clearly, that king is Rhaegar.

Tough to call it heads or tails on this one, but unless Rhaegar was incredibly naive and not very observant, he knew his sire was fond of pyrotechnics and cruelty.

Um...GRRM.

LOL! Not really. I won't pull the Turtle-Card. Hahahahaaaa

But it is rather apparent that Jaime is Rhaegar's man, and Rhaegar is not Aerys' man. Rhaegar is speaking treason, and rather than balk or bat an eye, Jaime is begging to go fight for him.

I'm not sure if you've read the Tuf Voyaging series, but in this case I think Rhaegar is realm-building Tuf, and Jaime is his kitten, Dax.

I think Jaime sees himself in Brienne. A sworn sword whose beloved king has died.

Yup. Here we agree, but I have a slightly different angle of looking at this. Given the name of the "kingsguard" it is easy to assume they are "guarding a king." It is a very obvious connection to make.

But, in each case we must neglect some intriguing bits of information in order to assert that is what they were doing. In the case of Jaime, we must forget that rather than guard Aerys from anyone, or let the rebels claim him, he killed him. In the case of the 3 kg at the tower long fallen, we must forget that they too - in spite of their heroic and sworn proclamations - allowed Aerys to die.

It is one thing for a single kingsguard knight to fail in his duties to guard the king. It is quite another for all seven to fail in the task.

If we take a step back and look at it critically, or even mathematically, one must consider the possibility that Rhaegar ensured Aerys would die. Let us consider his royal sire's kingsguard:

Aerys II Targaryen's Kingsguard (262 AC-283 AC) (link)
[Failure to guard the Mad King in red]

1. Ser Gerold Hightower, Lord Commander, also known as the White Bull. Killed at the Tower of Joy in 283 AC.
2. Prince Lewyn Martell, killed by Ser Lyn Corbray at the Battle of the Trident in 283 AC.
3. Ser Barristan Selmy, called Barristan the Bold. Fought in and survived the Battle of the Trident.
4. Ser Gwayne Gaunt, was killed during the Defiance of Duskendale.
5. Ser Oswell Whent, known for his dark humor. Killed at the Tower of Joy in 283 AC.
6. Ser Arthur Dayne, the Sword of the Morning. Deadliest of the Kingsguard in his time. Killed at the Tower of Joy in 283 AC.
7. Ser Jonothor Darry, killed at the Battle of the Trident in 283 AC.
8. Ser Harlan Grandison. Died in his sleep in 281 AC.
9. Ser Jaime Lannister, Ser Harlan's replacement. Survived the Sack of King's Landing in 283 AC, where he killed King Aerys II Targaryen. Also known as the Kingslayer ever since.

Of these nine knights, I must address #8 first. Ser Harlan(not of Pennytree)'s death sounds suspicious at face value, particularly in King's Landing. But he was old. Old men can die in their sleep. What is most interesting about him is that his death created a vacancy. This vacancy was filled with the appointment of Jaime Lannister to the kingsguard. We'll come back to Jaime, of course. But clearly, as honorable and true as Ser Harlan might have been, his death did little to guard and protect King Aerys II Targaryen.

And then there were eight knights... Before Ser Harlan's exit came Ser Gwayne Gaunt's, #4 on our list above. He is the only man on this list to have ever died guarding Aerys II Targaryen. Doesn't that say quite a bit about the remaining seven?

How does one guard a king with his life, then outlive that same king? That brings us to the seven white knights who "guarded" Aerys during Robert's Rebellion. (Which should really be called Rhaegar's Rebellion...but anyway...moving along.)

Rhaegar somehow came to command the Lord Commander of his royal sire's kingsguard. During the greatest threat to Aerys' health, #1 on our list, Ser Gerold Hightower was not guarding Aerys. He wasn't even in King's Landing. He was later found by Ned and his wraiths at a pile of rocks Rhaegar was said to have named the tower of joy, along with two of his sworn brothers.

Remember how many kingsguard knights Robert brought to Winterfell?

Yup. It seems Rhaegar traveled south with the same number. But again, I digress...

Sers #1, #5, and #6 of Aerys' remaining seven KG were sequestered in the Red Mountains of Dorne.

#1 Lord Commander Hightower died there. Rather than giving his life to protect Aerys, he was "Far away."

The same is true for #5, the Dark (humored) Knight, the bat-man himself, Ser Oswell Whent. He's the ser that pointed out Willem Darry was a good man and true (unlike them??) because he had fled with Aerys' wife and son. Is this a bit of black humor? Might Oswell be pointing out that Willem Darry is actually true to Aerys, while they are not? It is certainly difficult to assert Oswell was doing Aerys any favors in the Red Mountains.

#6 is the most formidable knight in the seven kingdoms, our suspected Lyanna-lover, Ser Arthur Dayne. While Robert was muscled like a maiden's fantasy, Ser Arthur Dayne was ending smiling knights and breaking lesser needles. He unsheathed Dawn, but the quiet wolf and little crannogman had no smiles to kill. Regardless of how easily his knees bent or did not bend, his knees did Aerys little good guarding that falling tower.

Of Aerys' seven, Rhaegar left three in Dorne to not-guard Aerys, and took three to the Trident to not-guard Aerys: #2 Prince Lewyn Martell, #3 Ser Barristan Selmy, and #7 Ser Jonothor Darry. The Dornish Prince was killed by Lady Forlorn (his paramour?), the Bold knight was injured, and the earnest knight who reminded Jaime to obey was killed as well. Whether alive or dead, all of them were quite literally "far away" from guarding their king.

Or were they?

It seems to me each and every one of them was doing Rhaegar's bidding, and doing it well. We can assume they merely sought to lay down some woe for the usurper on the battlefield, but that is not the same thing as guarding the king. Unless, Rhaegar was already the king in their minds.

It seems then, that the exception to of the seven must be the Mad King's ninth sworn sword, the Young Lion. The Royal Sire's Crutch.

Tywin suspected Jaime would kill Aerys. We must ask ourselves why. Why would Tywin suspect such treachery from his son? His son, who was Rhaegar's man and knighted by Arthur Dayne himself.

None of the kingsguard were guarding the king, they were guarding Rhaegar. Either Jaime acted alone on a whim, or he too was helping Rhaegar usurp his father.

Well, I'm not sure that is a detail Brienne would require. Brienne is sworn to rebels: Renly and Catelyn (individuals from two houses that united against Rhaegar's intentions - who betrothed and married a third). And Jaime is a Rhaegar-loyalist. It might be that he does not wish to sully the reputation of his king.

Exactly. And who was standing guard by the king?

I would argue that of the seven knights of the kingsguard, only Barristan might have actually been loyal to Aerys. And even his loyalty is not without some regret:

A Dance with Dragons - The Queensguard

Barristan Selmy had known many kings. He had been born during the troubled reign of Aegon the Unlikely, beloved by the common folk, had received his knighthood at his hands. Aegon's son Jaehaerys had bestowed the white cloak on him when he was three-and-twenty, after he slew Maelys the Monstrous during the War of the Ninepenny Kings. In that same cloak he had stood beside the Iron Throne as madness consumed Jaehaerys's son Aerys. Stood, and saw, and heard, and yet did nothing.

But no. That was not fair. He did his duty. Some nights, Ser Barristan wondered if he had not done that duty too well. He had sworn his vows before the eyes of gods and men, he could not in honor go against them … but the keeping of those vows had grown hard in the last years of King Aerys's reign. He had seen things that it pained him to recall, and more than once he wondered how much of the blood was on his own hands. If he had not gone into Duskendale to rescue Aerys from Lord Darklyn's dungeons, the king might well have died there as Tywin Lannister sacked the town. Then Prince Rhaegar would have ascended the Iron Throne, mayhaps to heal the realm. Duskendale had been his finest hour, yet the memory tasted bitter on his tongue.

/quote

Mayhaps it did not take his sworn brothers as long to see that Tywin's plan was the right one.

Who else?

A Feast for Crows - Jaime I
The day had been windy when he said farewell to Rhaegar, in the yard of the Red Keep. The prince had donned his night-black armor, with the three-headed dragon picked out in rubies on his breastplate. "Your Grace," Jaime had pleaded, "let Darry stay to guard the king this once, or Ser Barristan. Their cloaks are as white as mine."
Prince Rhaegar shook his head. "My royal sire fears your father more than he does our cousin Robert. He wants you close, so Lord Tywin cannot harm him. I dare not take that crutch away from him at such an hour."

/quote

Rhaegar is definitely the one calling the shots.

Most interestingly, notice that rather than leave Aerys guarded by more experienced kingsguard, or the one that had rescued him from Defiance before (Barry), Rhaegar instead decided to leave the one who is the son of the man Aerys fears most..the man who nearly roasted Aerys at Duskendale...the man who nearly put Rhaegar on the throne...

Not if Rhaegar knew his royal sire wouldn't be alive much longer.

And again, he could not have been planning a great council unless Aerys was to die.

Would they? I don't think Rhaegar would have much room for denial considering Aerys had acted upon this same rumor to surprised his son at the Tourney of Harrenhal but two years prior.

Remember this is the Mad King. He has already forsaken Rhaegar as his heir, and denied him his rights of primogeniture. He has taken his wife and children hostage.

If they marched Rhaegar up to their king, shackled for treason, I think Wisdom Hallyne would be summoned for Rhaegar, Elia, and their children... not Jaime and Jonothor.

And while Joffrey was a cruel bastard, he was a kitten compared to Aerys.

Not exactly:

A Storm of Swords - Jaime VIII

Jaime’s own page was scant by comparison.

    Ser Jaime of House Lannister. Firstborn son of Lord Tywin and Lady Joanna of Casterly Rock. Served against the Kingswood Brotherhood as squire to Lord Sumner Crakehall. Knighted in his 15th year by Ser Arthur Dayne of the Kingsguard, for valor in the field. Chosen for the Kingsguard in his 15th year by King Aerys II Targaryen. During the Sack of King’s Landing, slew King Aerys II at the foot of the Iron Throne. Thereafter known as the “Kingslayer.” Pardoned for his crime by King Robert I Baratheon. Served in the honor guard that brought his sister the Lady Cersei Lannister to King’s Landing to wed King Robert. Champion in the tourney held at King’s Landing on the occasion of their wedding.

Summed up like that, his life seemed a rather scant and mingy thing. Ser Barristan could have recorded a few of his other tourney victories, at least. And Ser Gerold might have written a few more words about the deeds he’d performed when Ser Arthur Dayne broke the Kingswood Brotherhood. He had saved Lord Sumner’s life as Big Belly Ben was about to smash his head in, though the outlaw had escaped him. And he’d held his own against the Smiling Knight, though it was Ser Arthur who slew him. What a fight that was, and what a foe. The Smiling Knight was a madman, cruelty and chivalry all jumbled up together, but he did not know the meaning of fear. And Dayne, with Dawn in hand… the outlaw’s longsword had so many notches by the end that Ser Arthur had stopped to let him fetch a new one. “It’s that white sword of yours I want,” the robber knight told him as they resumed, though he was bleeding from a dozen wounds by then. “Then you shall have it, ser,” the Sword of the Morning replied, and made an end of it.

The world was simpler in those days, Jaime thought, and men as well as swords were made of finer steel. Or was it only that he had been fifteen? They were all in their graves now, the Sword of the Morning and the Smiling Knight, the White Bull and Prince Lewyn, Ser Oswell Whent with his black humor, earnest Jon Darry, Simon Toyne and his Kingswood Brotherhood, bluff old Sumner Crakehall. And me, that boy I was… when did he die, I wonder? When I donned the white cloak? When I opened Aerys’s throat? That boy had wanted to be Ser Arthur Dayne, but someplace along the way he had become the Smiling Knight instead.

/quote

Rather than think of his own failures, he thinks Hightower could have included a few more of his accomplishments. And, though he laments becoming the Smiling Knight instead of Arthur Dayne, he also wonders if much of his romantic notions regarding his fallen brothers were due to him being fifteen, rather than things actually being as simple as they seemed in those days.

But you are right, he does blame himself for letting the vermin in...

He wondered what Ser Arthur Dayne would have to say of this lot. “How is it that the Kingsguard has fallen so low,” most like. “It was my doing,” I would have to answer. “I opened the door, and did nothing when the vermin began to crawl inside.”

While he takes the blame for allowing the vermin inside, he does not count himself as vermin. He could be talking about opening the door by killing the king, but as I've laid out, it's not like anyone of his sworn brothers were actually guarding Aerys in his time of need. Instead, they were all off helping Rhaegar's plans for a great council.

For what vermin did Jaime open the door?

Ned Stark.

For non-clever lions, maybe.

If one kills the king, sits on the throne, and flies the roaring Lion of Lannister over the ramparts...which is that?

Yup. I think House Lannister was on the losing side, and it clearly wasn't the Mad King's. Once Robert defeated Rhaegar on the Trident, the lion had to salvage the situation with false concessions.

Now, regarding messy feelings toward Aerys, and hurt feelings toward Rhaegar, consider this:  both Rhaegar's mother and Jaime's mother were rumored to have been raped by Aerys.

If it was a caucus race, maybe. Not in a monarchy. One does not impeach a tyrant. One does not hold a primary to challenge a king, let alone a Mad King.

Again, this only works if we are talking about a popular election.

Very intriguing questions. I don't think the finest knights in the seven kingdoms had much to fear from Aerys, though. I think it's more likely Aerys believed he had some support from his kingsguard. Instead, in his hour of need, he found himself guarded by a Lion.

Jaime snap? No, Rhaegar trusted his father to snap, and he trusted the Young Lion to be a young lion. After all, it had promised to obey...

It was either one hell of a risk to take, a desperate hope, or a perfect plan.

All true. But this is the same book boy who one day decided he must become a warrior. Was that because of prophecy? Or because he realized his royal sire was mad?

There is some interesting baggage between Rhaegar and the Lions. His royal sire lusted after Tywin's Joanna (and was rumored to have molested her). His royal sire had denied him Cersei Lannister as wife. His royal sire even disrupted up his great council planning meetings by crashing the Tourney of Harrenhal and stealing away Tywin's heir to Casterly Rock.

Quickly and repeatedly, we see Tywin and Rhaegar's interests aligned. Even Barristan remarks on this connection, and he isn't exactly the best of detectives.

I can't prove it, but I guarantee Tywin was behind the Defiance of Duskendale. Lions roar defiance, and one need only look at the Red Wedding to see how Tywin disguises treachery behind guest right when capturing kings.

LOL! Indeed. But, I do think Tywin and Rhaegar had many mutual goals.

Did he have faith in his son's mental instability, or his son's loyalty to Rhaegar Targaryen?

Just kidding, I have one more thing to add: The reason it matters if Dany were really Rhaegar's daughter, is that then the original prophecy could be true. Rhaegar's three children- Jon, Dany and Aegon- are the three heads of the dragon.
That's why it matters. Otherwise I'd say there is no reason for such a complicated plotline. Although GRRM has certainly given us hints that something is up with Dany's past...