You can quietly kill the vassals of your faction? (Mount & Blade 2: Bannerlord)

This situation. Every time we Story captured a new castle, then in its possession of a claim ONLY 3 people here and the same, others none. I'm one of those, our second king and third son of a noble warrior. Now the question is, is there a way to get rid of these competition? And they always have 60-70% support, I never the city will not get :D