I would argue differently, he stood up to several guys trying it on with his girlfriend at the pool, he's more than willing to listen to his mum and grandma and train himself to improve, he only gives permission for his mum and grandma and that's it (with the exception of the netorare character as he's been deceived into thinking she's not a futa). As for fucking others, that is something the girlfriend COULD grow into, the whole reason for Unit was basically for male on futa and/or futa on male stuff to be in there as well as getting round the incest problem (she stores the semen that's put in her, no matter whose it is) but admittedly I've gotten mixed feedback about that.
If you don't like the son, I anticipated some might think that of him, hence I made the 4 perspectives, you don't have to play as him. The son is basically a shy nerdy guy that got lucky, yeah his grandma and mum do stuff with his girlfriend but permission is there completely but his character growth was always intended to be through the story. Fuck it I won't put spoilers but the end result was I was gonna make him as muscular as his Grandfather and as smart as his grandma, with a kid that was entirely his (unless you activated netorare) and a stable loving relationship where Grandma will be gone by that point, Mum will be old then and it's a nice happy ever after. I wouldn't class a guy with a big house, a 6 figure income as well as a wife and child to be a loser in my view.
But look, I thought I'd answer, I'm not gonna argue, if this is not going the way you like I'll virtually shake your hands, thank you for being here thus far and I hope you find something more to your tastes to enjoy.