So my friend, as Scotland, just pressed a claim for someone in his realm against England for the duchy of york. He won, but the new ruler of york is independent. So he looks, he has a casus bell against this new ruler of the independent york. He uses it and goes to war. He finds himself in a three way battle for the duchy with England and Normandy. He wins again, but once again it goes to the member of his realm, but this member still ends up being independent.
I know I'm missing something really simple here, but if someone could point it out that would be cool.