I think Qin Che is his nephew not his son. I think his mother slept with the brother and when she saw Qin Changlan in a drunken stupor, decided to climb into his bed hoping that she could marry him, but it didn't go to plan. A man who is so inebriated that he is passed out can't get a hard on so how could he impregnate her if he couldn't do the deed. That's my thoughts anyway.