Byzantium is catholic. We agreed a union with the pope just before the turks take over constantinople.
Complete list of Catholic nations:
Rome
California
Comancheria
Brasilia
Levante
ooc: Its not. There were 2 unions with the catholic chucrh in RL. Also one emperor declared union, and his son, after the death of his father, declared that byzantium was again orthodox.
Right now i do the union, like the RL emperors did, about political reasons. I am the only nation in europe with orthodox religion and russia doesnt exist to help me and there is no balkan nation.
So i will be crushed and i will have no allies.