My King has just died. He had loads of brothers, so I didn't worry about hiers particuarly. The eldest brother has become King, but he is a little old - early 60's. When I check the "heirs section", all it mentions is his 7 year old son and a couple of Princesses. What happened to his brothers? I am sure they are still alive, in that their units are still there, but they are not down as princes anymore.
I would have thought they could be reagents or what ever. The crucial question is what happens if the current King pops his clogs before his son comes of age? - do I have a civil war? Considering that I rule over 60% of the map and only have Hungry and the Pope left to deal with, this could really ruin my day!!