So I managed to set up a few client kingdoms and instead of those factions behaving like my vassals they still continue to participate in diplomacy to such an extent that they simply dissolve my vassalship+alliance over them in case of me attacking a faction they currently are in alliance with, even though I keep our relations at perfect level by sending them back the tribute they send me.
Is there something to be done about this or am I going to have to get all genocidal on their asses?