I have to say this

But to prove it would be hard. Society would accept it.

Also I don't think he is the male lead because he takes over as the family head when he marries but to get approval for the marriage they would have to prove her marriage to his father wasn't fully complete. So once they make the claim then she would lose place as the family head and someone else would have to step in. No telling the headach that would come while she tried to prove her claim and she then wouldn't be protecting the kids like she promised.