His mum is domestic short haired, normal size. He is 7 months old, and already much larger than her. Actually, he is huge, in body mass, and looks even bigger due to his very long coat. He is totally domesticated but still very very aggressive, in that play normally turns to biting. I wonder if he has any wildcat in him. Is there a way of telling?
At 7 months old he is still more playful than an adult cat. Some bite harder than others, it is the way animals are. Most get over it, some never do.
Every cat has the genes of wildcat in them as that is their ancestry. Body size is irrelevant, and the long coat makes it even more unlikely that it is progeny from a wildcat cross.
You just have one big boy who likes to play rough.