Well, he's knocking up several women without any job and just the high school degree with the age of 20(?), so why should he not getting married? His financial life is over anyway if he starts to pay for the kids, his wife, and side wifes. Even if he won in the lottery. If he ever breaks up with them or more realistic the girls breaks up with him, they'll get the money. So, yes, he could marry one of them. His life was over as he pleased Heidi's breeding kink. MC isn't really smart. When the kids are born, the sex life will decrease. He should have fun with his harem for some years before knocking them up.