PS:
Since you cannot be sure that who this brother is who is studying with your son, insist that they not be alone together, ever.
This family has done your son a 'favor' by helping them get a car; this is undue influence, and while it probably isn't, it could be the beginning of grooming behavior to get your wife and son to feel kindly toward the brother.
(I am speaking from personal experience; a man, not a witness, weaseled his way into our family this way.)
I am not kidding; you can't know who this person is, and the elders may not know either, since the WT allows those who have abused a child to be used in positions of responsibility as long as the congregation doesn't know.