You are probably playing the censored version. You need to download the incest patch. They are all his family, Mrs Reigns is his mother, Iris his sister etc....I mean why developer took so much time to give a single sex scene in the game
It's not like the woman who leave with him are his family
According to Patreon
I have no idea how the game is without the incest stuff, but indeed, he only has sex with his mother on Chapter 10.