Me (M20) and my GF (F23) have been together for about 4 months now. I used to be a roommate in her house and we ended up dating. Her mom and little brother are like family to me, we do everything together and i always help them out. I just noticed that recently, her little brother has been doing some things that are pissing me off. He has adhd, so I was already used to him not listening, making messes, or not knowing personal space. But recently im getting tired of how hes acting with my girlfriend, he spends the whole day playing, complaining about being bored, or eating While me girlfriend works, and I chores and work, but recently, he's been changing thst behavior, with one detail, only when I finally try to spend time with her. He'll be in the living room building his lego (thats one of the chores we give him, and he complains about it) the second I go towards my sister's room, he follows suit behind, opens the door without knocking, and lays with us or in the middle of us. If I try to push him aside he says "I just want to be with my sister", if i leave the room, he leaves, if i go back, he goes back. Whenever we have to go to the gym, he starts "can you guys not go today, can we watch a movie please." And it will be that way nonstop. My girlfriend and her mom told me that they used to be 5ogehter 24/7 before me, but I noticed thst recently he only wants to be there when im there. Doesn't help that he makes comments that piss even my gf off but she doesnt say a thing, like "why is my sisi so fat" when she's had anorexia before. Its getting to a point that im almost resenting him, but i dont want to. I haven't complained about it to anybody, and I feel like I would be an asshole to demand that he doesn't spend time with her, but I also want time alone with my freaking girlfriend.