I'm going on 18 and have very mild Asperger's. Very borderline because I'm really bad at socializing in real life and I can get fidgety (flicking and holding things, wringing my hands, etc). My oldest 1st cousin has severe autism and has had a small-medium sized family dog for a long time now. Tmk, there have been few to no issues. He has also been to my house a couple times (a lot of animals) with absolutely no issues. His condition gives him a speech impediment and massive social problems (practically can't socialize at all), but his intelligence is far ahead of his peers.
My point: I'm guessing your brother is pretty smart (relatively speaking). He can't use something related to intelligence as an excuse for autism, because autism does not block out things mind related.