and the, well, the mechanics of a relationship have to have worked out previously for that family tree to have not ended. the horned ancestors have non-horned partners so there's gotta be some trick to it.
If the woman is the oni and her partner is a human male, making her pregnant is not a problem: he can take her doggy style.
There's a fatal flaw in this premise.
When she gets horny, her horns come out.
The more horny she gets, the bigger the horns get.
The bigger the horns get, the stronger and more dangerous she becomes... because her strength gets more and more uncontrollable as it keeps increasing.
Oni kouhai will never be able to make love to her senpai without accidentally killing her. >_<
Solution: Senpai is an oni too, but only finds out after being confessed to by oni kouhai.
