I think my brother has Asperger's?

My younger brother has always been ‘strange’.
He is very withdrawn and doesn’t have many friends. He always sits in really awkward positions, constantly plays with the strap on his watch and chews his tshirts. He wouldn’t even tell me or his own mother what universities he was applying to, or what subjects he was interested in, stating that that was his business.
You really have to make an effort to have a conversation with him.

Last weekend I made the effort and took him to a few pubs with me and my friends (he has just turned 18), and after about an hour one of my friends who works with children and teens with Asperger’s told me he was almost certain he had the condition.

Later that night, my brother went home early and must have continued to drink on his own because he had been sick in his bed.
Me and my parents tried to wake him up and change his sheets for him and he attacked all three of us. Punching and biting.
The next day he acted like nothing had happened and showed no signs of remorse.

Does this sound like someone with Asperger’s syndrome?
And if he has it, how would we go about getting him tested for it?
He is an adult in the eyes of the law now, and he most certainly wouldn’t agree to go and get tested.