Yep. A prince...two actually.

I'm playing as the HRE and the Almos had a civil war, and 2 princes were part of one revolting army. I successfully bribed the army (no "You can't bribe princes!" message) and got both of them. They also didn't revert to their original names, they kept their "prince" names--"Prince Abdul," "Prince Hassan."

Which brings me to another subject. In a civil war, if the rebels "win," i.e. wipe out the loyalists, is the faction then controlled by them, or does it cease to exist and the rebels function like the rest of the generic ones?