I have a duke who has a married a foreign duke which has given me an inheritance warning. This being Crusader Kings, my gut instinct is to have someone killed but I'm not sure who or in what order people must die.
The breakdown is thus: I am playing a Byzantine emperor with high crown authority (shouldn't that prevent titles from leaving the realm?) with a male duke of Jazira reporting directly to me. He has married (non-matralinially) the duchess of Orkney who is a direct vassal of the King of Norge. They have two male children together.
My first thought was to kill my own vassal duke so that his son inherits his duchy and the son becomes my vassal. Then when his mother dies he inherits Orkney which becomes part of my empire since he's already my vassal (at least I think that's what will happen). That's when I noticed a final confusion in the matter, the duchess and duke have different heirs. Their elder son is the heir to the duchy of Orkney while their younger son is the heir to the duchy of Jazira.
I am guessing this has something to do with the differing inheritance laws of the two duchies, the duchy of Jazira has primogeniture succession while Orkney has gavelkind.
All I want is to keep the duchy of Jazira under my control, I don't want Orkney, I have enough problems as it is without it. Who should die to make sure this happens? I suppose I'd accept non-murderous solutions as well, there's a first time for everything.