I think that its very unfair to call them idoits... You don't know thats the only reason. Keyhole judging try not to do it...
I did quantify my opinion by saying "if that was the reason" they disowned him. And I'm generally far from judgemental, but from what Dianne has said it sounds as though the parents have dealt her nephew a very raw deal.

Apologies Di if I've caused offence by referring to your BIL and SIL in this manner.