Monica took the words right out of my mouth. If he bites your hand every time .. heck at least for now don't push it. Sounds like lil birdie selected the 13 yo to be his BFF. Many birds will do just that. Question? Does he have to accept you also before you can provide him a home? Can it be enough that he trust your son? Weeks or months down the road he may relax a bit more but there is no safe bet. These creatures have triggers, protect the nest, protect their mates, protect toys/food etc. which may all result in a bite. It is possible to socialize the bird so that its not on defensive all the time and it would be rare indeed if he would become everyones cuddlebug. It CAN happen but its rare.
And oops... forgot one very important thing. NEVER take getting bit personal.