Viking conquest King help

[KonnungrThor]

I need your help i conquered Ribe then i saw quest that gives me task to be king of all over scandinavia but i made my vassal as ruler of ribe what can i do to be ruler?

 

[WhiteEyedSh4rk]

I need your help i conquered Ribe then i saw quest that gives me task to be king of all over scandinavia but i made my vassal as ruler of ribe what can i do to be ruler?

You can accuse him of treason and then give Ribe to yourself. Though It might be enough to conquer the cities once and don't necessarely keep them, to complete the quest.