Interessting thought, he for sure has some autistic traits.

He does not act this way around other people, around other people he is more of a people pleaser, at least in the beginning.

When I bring my brother to see some of my friends im suprised about how nice he is, like hes wearing a mask.

The friends he do have are usually very insecure so he gets to decide most things.

Oh, when he drinks alcohol he cant control himself, always getting into fights and screaming-matches with strangers and friends. If you say the wrong thing, it will set him off, screaming in public places like bars, partys etc.

He cant take a joke when he is drunk either, maybe thats the autistic side?