A question:
When I want to declare war on someone to vasssalize him (Vassalization war) I can select 1 or 2 of his titles, e.g. a count and a duke title.
Those titles will be vassalized to my highest or main title (ic. King of St. Pierre).
BUT
I want to vassalize those titles to another Duke title I own. Why can't I select my own title to vassalize the other party to?
Or do I do something wrong and it is possible, but I just don't see it?