Hi~ Aerys moved the royal court to the rock right? Shortly after Jaime & Cersei were born? Eventually he moved it back to king’s landing but ifwhat if he hadn’t? What if he’d moved Rhaella & Rhaeger into the rock with in with the intent of just living there as long as he wished? Would Tywin be able to demand he leave? What if Aerys refused?

joannalannister:

Yeah, Aerys moved the court to Casterly Rock. He took Rhaegar with him:

in 266 AC, at Casterly Rock, Lady Joanna gave birth to a pair of twins, a girl and a boy […]. The following year, 267 AC, saw the death of Lord Tytos Lannister at the age of six-and-forty. […]  With his passing, Ser Tywin Lannister became the Lord of Casterly Rock and Warden of the West. When he returned to the west to attend his father’s funeral and set the westerlands in order, King Aerys decided to accompany him. Though His Grace left the queen behind in King’s Landing (Her Grace was pregnant with the child who proved to be the stillborn Princess Shaena), he took their eight-year-old son Rhaegar, Prince of Dragonstone, and more than half the court. For the better part of the next year, the Seven Kingdoms were ruled from Lannisport and Casterly Rock, where both the king and his Hand were in residence. 

The court returned to King’s Landing in 268 AC, and governance resumed as before…but it was plain to all that the friendship between the king and his Hand was fraying.

I don’t think Aerys wanted Rhaella by his side at this time. 

I only have the most rudimentary understanding of feudalism and medieval history, but I think if the king really, really liked your castle, the owner could “gift” it to him / the king could seize it. For example, Wolsey ~”gifted”~ Hampton Court Palace to Henry VIII, as I understand it, because Wolsey was on the outs with Henry. (Somebody might wanna check my facts here, cuz I don’t know a whole lot about it.)

So yeah, I think Aerys could live at Casterly Rock indefinitely if he wanted to. What a king *could* do and what a king *should* do politically aren’t always the same thing, though. It was really expensive for a king and his court to be your guest, so that would cost Tywin a fuckton of money and that would really only be something you would do to your political enemies (which is probably why Aerys did it for half a year, imo – idk I think it’s almost like a way to tax someone you don’t like that much). And if Aerys formally claimed Casterly Rock for his own, when Tywin hadn’t done anything, that doesn’t set a good precedent for the other lords in Westeros. The Rebellion happened because Aerys denied his lords due process under the law, and I think something like seizing Casterly Rock unprovoked would be viewed in a similar light. 

This might be a better question for @racefortheironthrone, because I’m not sure if I’m totally right here. 

This is mostly on track. A few clarifications:

1. It’s not quite the case that you could see your castle seized period; there had to be some specific legal pretext to justify the king taking your property. In this case, Wolsey had to give up Hampton Court in part b/c it had been a royal gift in the first place, although obviously he lost all of the money he put into the place (installing running water, glass windows, etc.).
2. In terms of royal occupation, I suppose technically a king could stay indefinitely, although it’s important to note that there’s a big difference between being a guest (even a permanent one) and seizing the castle for one’s own: right to incomes and feudal services, legal jurisdiction and so on, as long as the owner couldn’t think of a pretext to get rid of them. But if a pretext was offered, it would be very hard socially for a king to refuse.