Another question about dejure kingdoms

[Jore]

I am currently playing game that I orginally started as Colovian Estates. I formed kingdom of Cyrodiil and later Skyrim then captured Rihad and formed Empire of Tamriel. During this process I actually left most of Kingdom of Nibenay alone only taking 1/3 of its provinces. Now I conquered it with Imperial Conquest cassus belli. Now I am stuck with him as my vassal. Then I decided to usurp his tittle since I wanted Nibenay to get joined into kingdom of Cyrodiil. My actual question is how I do this? Do I have to destroy tittle first?

Sorry about my bad english. I hope you guys understand.

 

[Alyiakal]

The petty kingdoms should be absorbed into their respective high kingdoms if you control all the territory and duchy titles (no one outside your realm is holding any of its duchy titles). This may take a few months, although it usually happens by the time the next month rolls around.

 

[exin]

Aye, usurp the Nibenay title, then control all the duchies and the Nibenay title should automatically absorb into Cyrodiil the following month or so.