Cat is Biting/ scratching...No idea whats up?

So i got a kitten from neglected household(smelled like urine, super dirty, fleas, etc) at the time the kitten was weened and ready to be taken so i gave him to my mom. She treats this cat (whos a year now) like a king- house is always super clean, he has all his shots, flea meds, good food, alot of toys, she gives him constant attension and plays with him until hes tired with his cat toys. about 6-7 months he started biting(hard) and scratching not only people that come over but people that live in the house(including my mom). Nothing in the house has changed no new pets, no moved furniture, we have cat toys and cat posts so he has height. Everyone is always gentle with him. my mom has a loving dog who the cat has gotten along with since the day hes came home. he just gets in a mood to attack when he feels like it terrorizing my mom and i feel bad for her lol. When he was young we made sure to keep our toys and hands separate so he didnt attack and confuse the two. There are no animal smells on me when i come over. He seems healthy to me from watching him over time. Is this just a personality or ? Any ideas??