Yes, I was very confused about the whole situation, especially as there was no sexual chemistry between them before or after and they just abandoned the children and never spoke of them again. Like ..."you do you think the kids are doing?"
My headcanon is that after he accidentally got knocked up, he just sorta figured there was nothing he could do to avoid accidentally having sex, so what's the harm in doing it intentionally? At least that way it's easier to recognise all aspects as consensual.