Is there any way to make alliances with other powers other than through marriage? I've been in several situations where it would be great (and not unrealistic) to form an "enemy of my enemy is my friend" alliance against a larger power that is threatening me and a neighbour (such as my Oghuz nation and Khiva vs. the Seljuks) but I can't find any way to ally with them other than by marrying one of their nobles, and this isn't possible because Khiva is Muslim and my character is Tengrist, and the "Must not marry infidel" mechanic is getting in the way.