Inheritance question
I'm a king
I have a son (who is also a vassal of mine, a count) who is married (regular marriage) to a lady who suddenly inherited a large duchy that her father detached from the parent kingdom (not mine). So the wife is now a ruler (duchess) of an independent realm.
Their son is heir to both the county X (my son's county) and to the duchy of A (the wife's realm). And I keep getting the warnings of "problematic succession".
How can I manipulate the situation so that my son's county will remain in my realm, and (if possible) bring that large independent duchy into my realm as well, through inheritance?
I've seen (somewhere in this thread) somewhat similar case, where things didn't go right, and one "fix" suggested there was to make the person in the line of inheritance (i.e. in this case my grandson) a direct vassal before he inherits the independent realm. Would this work? Would a simple count suffice or would he need to be a duke, considering that the other realm is a duchy (actually two duchies but the other seems to be the "main" duchy)?
Any thoughts? I really would loathe to lose a county smack in the middle of my realm, and I can't rely on sheer force since the independent realm is relatively well-to-do, has quite a bit manpower, and could probably fight me to a standstill.