Heredity might be something - I would call my father limit autisitic in the sense that he does not care at all for what people answer him and is unable to react to other people's feelings. But maybe he is just unsensitive... We also have a case of schizophrenia in my close family, but in this case traumatic child experience might play a role.
Sidonzo - I thought like you when I read about Jonathan, he sounds a lot like Marc.
For the moment, my sister tries not to give up on the grand-parents - after all her ex-husband got the message after a while and admits that Marc's problem does not come from their divorce or his education. And he refused to see it for a while too. She does not want to separate the little one from his father - and this means that he will meet his grand-parents regularly.
Also, Marc's therapists says that he is too young to make a definate diagnosis, that he might be an Asperger child, but that it is as dangerous to put a diagnosis so young on a child as to pretend he has nothing. What do you think of it?