As you have not provided much info, this answer is somewhat based on conjecture.
It sounds as if your child is neuroatypical. Whatever the condition, he does not like the feeling he experiences (either physical or psychological) when someone hugs or touches him. For some reason, he doesn't welcome touch, and he 'fights back' when someone violates his space. And, again for some reason, instead of expressing his wishes/feelings verbally ("Please don't hug me. I find it very uncomfortable."), he bites.
The message is clear: Don't hug him. Don't initiate any uninvited touches.
What if you have a sixteen year old the still bites?
I would stop touching/hugging him, I would speak with the teachers and counselor at his school, and I would have him evaluated for a neurological problem (maybe a sensory issue). You may have done all of this already.
If someone had severe trigeminal neuralgia where just a kiss on the cheek resulted in a jolt of severe pain shooting through that side of their face, would you still want to kiss them on that cheek? My guess is that you would understand and of course you would avoid that.
Neuroatypicals don't experience the world the same way that neurotypicals do, just as people with trigeminal neuralgia do not. Understanding and respect is in order. Unless he initiated the biting out of hostility/frustration/other, the answer for the moment is to stop touching him in a way he finds uncomfortable, and work with him and a specialist to get him to communicate his desires in a socially acceptable manner before biting is triggered.
Work on the specifics with your doctor/therapist. That's what they are there for.