Sadly, my parents never knew I had Aspergers when I was a kid, it would have saved a lot of family arguments and 'tantrums' from myself if we had.

The one thing I would suggest, is tell him he is on the spectrum, explain exactly what that means and give him as much information as he can digest about it. The reason I say that is because I always knew I was different to other kids, I just didn't know why, by the age of 11 I was starting secondary school and my life went totally upside down at that point because of the massive change to routines, class structures, social circles etc. Had I known what I was dealing with and why I was different, life could have been a lot easier.