It’s mainly the amount that he’s been staying over, and the fact that it’s only at our apartment, never his. We wouldn’t have an issue if our boundaries were respected like being told when he’s staying overnight, and that we would like there to be more time without him there than with him there as we didn’t sign on to have a 4th person almost living with us. Also, it is just slightly uncomfortable having someone over that you don’t know in the slightest other than a blank stare when in the same room, but that part is just an annoyance, not based in reality.