Meet Khaireddin. He's dead now.
However, back in the day, he was the (adult convert?) Count of Orania, and one of my vassals, my Kingdom being that of Aquitainia, Navarre, Africa, and Mauretania. What happened was that he declared a Muslim sultanate or whatever in one of my lands and I defeated and vassalized him.
Apparently, his father was Muhammad (tee hee) of Mecca, who ruled the Emirate of Medina.
During one of my wars with them, at some point I must've killed him through battle and so the newly Christianized son became Duke of Medina.
Right now I own enough of the Hedjaz to be considered Duke of Arabia Felix. I don't own Mecca itself yet, however. The point is shouldn't there be something that kicks into gear when a Christian (or, in a gonzo game, a pagan) takes control of the holy cities of Islam? Shouldn't a Muslim equivalent of crusade kick in? Or maybe a special attribute that makes all of them have a vendetta against you? Maybe if you loot the holy cities your BB goes up for religious enemies?
However, back in the day, he was the (adult convert?) Count of Orania, and one of my vassals, my Kingdom being that of Aquitainia, Navarre, Africa, and Mauretania. What happened was that he declared a Muslim sultanate or whatever in one of my lands and I defeated and vassalized him.

Apparently, his father was Muhammad (tee hee) of Mecca, who ruled the Emirate of Medina.

During one of my wars with them, at some point I must've killed him through battle and so the newly Christianized son became Duke of Medina.
Right now I own enough of the Hedjaz to be considered Duke of Arabia Felix. I don't own Mecca itself yet, however. The point is shouldn't there be something that kicks into gear when a Christian (or, in a gonzo game, a pagan) takes control of the holy cities of Islam? Shouldn't a Muslim equivalent of crusade kick in? Or maybe a special attribute that makes all of them have a vendetta against you? Maybe if you loot the holy cities your BB goes up for religious enemies?