Is it normal for my boyfriends mom to act this way?

I feel like the reason he does fall into what I think it's her trap, it's because she knows he felt responsible to making her and his sister happy when his father passed away. He constantly makes sure she won't get upset, takes her laundry from the drier and folds it, she constantly asks him to bring things for her, he bought her a car and pays half of it, he pays half her Victoria secret credit hard and he pays almost all the rent. His sister is 20 and doesn't have to pay anything. He brings his mom flowers more than he ever brought me. What put the cherry on top was that she walks around in her sports bra and short shorts, his friends say she's hot, even flirt w her...I don't know if she's being a normal mom where she wants her sons affection and be #1 forever or if she thinks of him as his dad, and sees him more than a son, she did tell me that once crying, when I had a fight with him. I didn't question it. I feel he is afraid to upset her, he has told me so, and didn't want to move out because he said they all have a close relationship. I feel that he wants to make me happy too, and he puts time in our relationship, but his mom is holding on tight and he feels guilt if he lets go. But I just don't know if his mother sees him as if he was the dad, they look alike.