I'm playing as the King of Scotland. I discovered a plot of the Duke of Galloway to lower crown authority, I attempt to imprison him, but he revolts. As I'm sieging his capital he dies, his son succeeds him, the war ends, but they do not rejoin my realm; his son is now the independent Duke of Galloway and The Isles and I have no claim to bring him back into the kingdom. Am I correct in assuming this is a bug?