Howard had the very same issue when he was a kitten. We adopted him from a local rescue when he was only 13 weeks old, and he went from sharing a space with 15 other kittens to being an only child... so he began viewing my boyfriend and I as his "litter mates". He bit and scratched and attacked, but he was "playing" with us....or "playing" as he viewed it. To put a stop to this, everytime Howard's behavior got out of hand, we (whoever he happened to be attacking/"playing with") would gently grab his scruff, say "NO!", and gently hold him in place so he couldn't squirm away until he calmed down. We didn't hurt him. We just did kind of what a momma cat would do when one of her kittens was out of line. After several months of this, Howard began to understand that we were not his litter mates, but his parents, the "alpha cats" of the household. Now Howard never bites or scratches or attacks us anymore. In fact, three years later, Howard has become a very, very, very affectionate cat and loves to sit on our laps and get pet for long periods of time.

The only reason Howard ever attacks/plays anymore is when Luna antagonizes him when he's sleeping or just doesn't want to be bothered...or when he wants to initiate a game of Cat Wrestlemania with her.

I hope that helps.