I was re-reading the part where Theodore finally names his heir. In it, it is stated that there was theory he wanted to name his niece Elisabeth, given she was his favorite, and that is why he went with her husband. Is there a reason, since they were married, that he couldn't have named them both in their own right similar to William III and Mary II of England? Also, there was mention of not naming Elisabeth because her non-bastard half-brother may have tried to take the throne. That makes no sense to me because Theodore was literally able to name anyone he wanted. Sure, naming his niece over his nephew may have been weird, but because it wasn't following traditional inheritance principals, he was literally naming his successor, would Charles not have much of a leg to stand on if he wanted to challenge it?