Fallen angels with a breeding kink.
Angels aren't usually capable of reproducing, so the angels that like to get a little frisky can do so without consequence. It's something done for pleasure, a harmless bit of fun. But angels that are stripped of their titles and cast down to the Devildom, they learn quickly that everything's changed. Their bodies, their morals slowly chipped away in a bid for survival. The meaning of sex and intimacy changes too.
For fallen angels that weren't capable of creating life before, now they have that possibility. It's power, new and potent, a way of marking someone as their own, in a way no one else ever will if they have any say about it. It's possessive, almost animalistic passion, the overwhelming urge to claim someone as theirs, to be bound to them forever, in a way that wasn't possible before. Some of them might be enticed by the idea of offspring, some of them might not be. It doesn't matter - it's the defiant act itself, the freedom to choose that path if they want to that matters. It's a choice they never had, but now it resonates deep within them, satisfying some of the most primitive and instinctive urges of their newfound sin.
(And if they get a little petty satisfaction knowing how furious it must make Father to realize this truth, that they can still find new ways to defy him where they're no longer touched by his punishments, maybe they keep that to themselves.)