Hi fella,
Our 7 year old son, Cameron, has Asperger's and as a parent, I know how it feels to be in denial towards your childs condition, so I would approach the subject very carefully and in a way that shows that you only have your Nephew's well being in mind.
Once that mountain has been climbed, it would be good to get him properly diagnosed, it's not a process that is at all taxing or stressful for the child, in fact, when Cameron was diagnosed, the process was treated like a game and he quite enjoyed it!
The diagnosis will not only provide your family with a reason for your Nephew's behaviour but allow them to understand, make allowances for and be better prepared for any outbursts etc as he gets older.
I notice that you're in the States, so obviously things will be very different, however when Cameron was statemented it also provided the educational authorities in his small village school, greater funding and further help with Cam's educational needs.........ironically, his condition means that academically, he's way in front of his peers in both literacy and numeracy.......he just doesn't want to play with them come play time!
We found the studies of Dr Tony Attwood very informative, he is a leading authority on Asperger's Syndrome. His books are readily available from Amazon etc, but to be honest, the first step is going to be speaking to your Nephew's parents, then having him diagnosed.
Sorry to ramble on, but I hope some of it has been helpful.
