Nice excuse there, Fennah. I still believe they are thicc because he’s attracted to the OCs as well. Also, based on his character’s mating process, it doesn’t seem like they are mammals. With the loser getting decapitated, and then birthing babies after being in a cocoon of cum, it seems more like an insect mating ritual. Specifically, with the
Mantis, which uses sexual cannibalism during mating. The difference between this and his OCs though, is that the OCs never die after decapitation (due to immortality). For mammals, they usually have fewer babies, and they need to be reared by the parents much longer. If this is truly the case, and his OCs are based off of mammals (hence mammary glands on the females), then the reproduction should be similar to how mammals reproduce.
Of course, I’m no scientist, so Fennah needs to answer for this, as he knows science.