Not possible for anyone to impregnate girls except you.
For once, I'd make an exception to my aversion and say this is the type of game where I wouldn't mind having this feature. As I wouldn't mind if your slaves and wives could "cheat" on you. You're "da boss". Absolute power. You can execute them, punish them or act like a benevolent pater familias, that just wants his household to be happy. In that scenario, I don't feel those things as humiliation, as much as morale management. You already even have the mechanics in place to simulate a reputation hit if you're cucked when you throw a pool party or a similar event, maybe an end-of-day event if certain parameters are met - just make it a one-time influence hit per event - but make it manageable.
So, impregnation. Same thing, I hate that shit in most games (possibility of your LIs to be impregnated by other guys) but here, you could make it work in your favour, as in using bulls to have your own eugenics program and try to breed a generation of super humans. Like the ancient Romans, who cares about your genes, choosing an heir is about picking the one that would best carry on your name and legacy. As for the rest of the offspring, yours and others', it's just your manpower expanding. Better do it with quality in mind
