Any combination of Len, Mick, Barry--Crusades era AU (I suppose similar to your fantastic Anchorite fic)
Well, since I’ve already done the Anchorite fic (glad you liked it!), let me try something different.
1 - Mick is the third-born son of a very rich family who has a bit of a problem with lighting fires all the time, making him a fairly serious threat to their townhouse and the surrounding city (made of wood!) or the farmland around the castle. As a result, they decide to send him to become a priest. Mick has zero interest in religion. This does not stop them. Mick is a bishop now. He is super unhappy about this.
2 - Len is a Jew that got brought in for conversion-or-death for one of Mick’s newest and ends up having a chat with Mick about how religion sucks. It’s somewhat startling for him to realize he’s talking to the bishop, mostly because that doesn’t come up until after they’ve slept together (Len thought he was going to die - may as well die for sodomy as for Judaism, honestly).
3 - They end up running away together to join the Crusades, because Len really can’t stay where they are at the moment (people might get suspicious as to why the supposedly converted Jew doesn’t seem all that converted) and Mick likes the idea of being the sort of bishop that lights things on fire.
4 - Barry joined the Crusades as a cook because he is neither nobility nor rich, but he’s not a serf, either. He left his hometown because the love-of-his-young-life (Iris) made a very favorable match with one of the city elites (Eddie) with whom she is actually in love, and while Barry totally supported her, he also did not want to stick around for the wedding. He hopes it will pay for a pilgrimage somewhere to pray for his father’s release from prison, which he believes is wrongful. He’s assigned to cook for bishop Mick and his ‘valet’ Len.
5 - Mick and Len adopt Barry because he’s the only one who calls them thieves right to their faces, which they find charming. They are, of course, but no one ever says as much. They end up travelling all over and Mick is eventually recognized by the Pope as being particularly heroic (he blew up a gate, thereby permitting a city to be taken) and manages to finagle a church-blessed pardon for Barry’s dad.
6 - eventually they settle down somewhere. Mick is still the world’s worst bishop, but Barry makes friends with an order of (rather militant) nuns and they settle into a very happy relationship that involves inventing new types of artillery while not interfering with each other’s lives. Everybody knows not to ask Mick any questions about religion, but they all write very nice things to the Pope about their “most holy bishop” being excellent. Mick’s family is pleased, albeit confused. Len quietly organizes the town to be a safe space for Jews trying to avoid persecution. Their town becomes very popular as a result. Not every town where the bishop is best friends with a Jew, after all, and it’s very hard to justify persecution when the local bishop is against it.