Whoa! I'm way out of the loop here. See what happens when you go away for 5 days...

I agree with econ with regarding the four houses. I think having the four Duchies controlled by the king's children is fine. Remember that many of the major nobility had blood-ties to the ruling king, and one of the houses won't be controlled by a blood heir, because it will be the princess' husband.

Regarding civil wars, I hope that we can engineer more petty disputes, which result in a quick battle and then a political settlement. But they shouldn't occur too often.