After one listen, I like this a lot. Also just read:
[Papa Emeritus IV] is stated to be the first frontman to not be a part of the Emeritus bloodline, though it is heavily implied he is the bastard son of Papa Nihil and Sister Imperator.
I can't follow the lore of this band, and I still love it!
Well, for the first three albums there were Papa Emeritus I, II and III, they were all children of Papa Nihil - you might remember him from his sax solo appearence during the latest tour, he's supposed to be the head of the whole clergy thing.
Then for the fourth album they introduced Cardinal Copia, the character for the entire Prequelle tour - at the very last concert, spoilers I guess, Papa Nihil died during the sax solo and Cardinal Copia was dressed on stage by a bunch of nuns and anointed, mid-concert, as Papa Emeritus IV, so he's the same character who got "promoted".
The whole "he's the bastard child of Papa Nihil" comes from wacky YouTube short videos that were released during the Prequelle cycle, adding some comedy moments to the lore and creating a backstory for the whole clergy thing, and yes, that was the implication.