He’s her Bull. Has nothing to do with respecting your family. He’s setting the tone so both of you know he’s the Alpha Male.
That is apparently what she wants because like you said.. She’s not going to stop fucking him.
And she likes two men fighting over her.
I actually had a similar situation many years ago. The guy got so jealous he pulled a knife on me. In HIS mind I was fucking his wife without a condom. After I disarmed him and put him in place, I laid his wife on him while he was on all fours. Only then did SHE remove my condom and I made sure that he knew why and that I wouldn’t be using them from then on. His concern was her getting pregnant because she wasn’t on birth control. She decided after that first encounter that I would be calling the shots. On our second date she told the both of us she was ovulating. I ALMOST felt sorry for him when I told him that she was staying with me for the weekend. She didn’t get pregnant that weekend but about three months later she did. That’s when I found out he hadn’t had sex with her since that first night when he got stupid.