I also remember another mod, in which titles would be awarded to the Faction Leader when the faction would hold a certain number of provinces.
i.e. Zaragoza & Barcelona = King of Aragon
Salamanca, Leon, Burgos & Toledo = King of Castille
Basically, this mod (Anno Domini) would in essence give bonuses to the faction leader by being ruler of Kingdoms. And, in a way, ensure that your faction leader is always kick ass =). And, finally, it would be defined by actual Kingdoms, Duchies and Counties. So you could be Duke of Toulouse, King of Castilla, King of Navarra by holding Salamanca, Leon, Burgos, Toledo, Pamplona, Toulouse. Minor bonuses in all of this and they stack up.
Just thought about throwing it out there since Velasco Garcia is some a-hole and shouldnt be holding my damn King title.