"In California, he is held forever liable even if it's not his kid. I don't think they even care if he signs the birth certificate or not."
If a divorce occurs, can the man get sole custody?
I actually know someone this happened to. His wife had 3 kids before they got married. The youngest wasn't his. She made a big production of it during the divorce. He ended up with all the children anyway. She eventually ended up in rehab for alcoholism.