care to elaborate on that sister kingdom comment? It pops up from time to time but seems more like speculations to me.

Some of the high ranked kingdoms might have semi allies, but I wouldn't count to much on those relationships with all the gutting going on in the top these days, feels like half the kingdoms up there disbanded and reformed with others under a new name just the past few ages, that probably have more to do with requirements and leadership than anything else, if you put the most active 25 province kingdoms on 20 provinces that means the other 20 province kingdoms will have to raise their requirements in response or fail to be competitive.