
Originally Posted by
knppel
I would not recommend giving out any Duke title without granting all of the duchies de jure terriotry as vassals to the Duke (if you want to manually install his mayors and counts, do so and transfer the vassalage afterwards).
Specially if you yourself hold counties in his duchy, his anger will aim towards you (while messing up duchies vassallage between your Dukes only makes them fight each other which is admittedly less worse then them revolting).
Solution if you hold Duchy titles you wish to disappear: select one guy you want to get rid off, and who owns one county. Grant himm all the Duke titles, but make sure he has no Vassals. (So, you have to hold the counties yourself or have vassals installed in them before granting the Duchy).
He will hate you as so much of yours should be his by right now, but that doesn't matter. Quickly start the plot to revoke his County title.
He will not agree to that, so be sure to have your levy in his county when sending the letter.
Once he declines the revocation, siege his stuff, and usurp the County. The Duchy titles will disappear, you will have to create them again (which you obviously don't want, as they would just awaken your vassals envy)