Quote Originally Posted by Martok
Influence (faction leader only): If your king/sultan/emperor/etc. has a high Influence rating, it increases the likelihood of your faction being able to secure alliances and marriage proposals. A high Influence rating also seems (although again, I've never seen conclusive proof) to reduce the chance of another faction attacking you.
Adding that influence affects the hiers stats a lot.

Quote Originally Posted by Martok
Usually, the rebel general with with the highest command rating is selected as the ringleader (and your new faction leader should you choose to back the Rebels in the civil war). Generals of royal blood are sometimes ringleaders as well, but I don't know if they get preference over "non-royal" generals with a higher command rating -- I've not really paid attention to that in the civil wars I've gone through, to be honest.
Royal blood (even ex-hiers that been "dead" for hundreds of years) got the highest preference.