When writing fantasy hierarchies—royal, noble, religious, etc.—you don’t need to stick to pre-existing titles and hierarchical structures.
If your system allows for same-sex marriage, perhaps there is a specific title or titling system for the consort (the one who married in). There may be a King and a Queen Consort or a Queen and a Prince Consort (or King Consort or Prince), but you could have a specific alternative title for the Prince Consort when you have a King or the Queen Consort when you have a Queen.
If the King or Queen has multiple official spouses, they can have different titles that denote different levels of rank, importance, or chronological joining the family. If there is a harem or are concubines, they may have different titles, either from each other or from the official spouses.
Appointed nobles can have different titles than those who are noble based on familial ties to the royal family.
Titles can be based on types of landholding, geographic location, or other characteristics.
There can be innate titles and given titles, as well as titles that can be taken away.
Religious titles don’t need to match Christian religious titles, and religious hierarchies really shouldn’t look Catholic unless you’re writing about Catholicism.