Specifically from a Non-Christian religion. I'm thinking of religions similar to the ones practiced in ancient Greece and Rome. Would you (as a writer) just use Father, Mother, Brother, Sister, etc. or is there another title that can be applied? Is there any reference to what they were called in those cultures? Your Holiness seems a bit too 'high-tier' for your run-of-the-mill priest. Also, how would you refer to a tribe's shaman or religious leader if he was from a tribal culture instead of an organized religion?