Not a reverse.
I know someone who has had a baby after having an affair with a married man. She went out to get pregnant as she wanted a baby, and he had a wife and children so it's destroyed their lives. The father is not involved at all.
I think the man is a slimeball but I can't help but feel very disapproving of her too. My father had an affair and it would have been devastating if this had resulted in a half sibling too. I wish I wasn't such a judgey cow but we can't help some things can we?