I've known an autistic kid for years and, honestly, she plays any and every piece of electronics she can get her hands on with no problem. She got interested in the games her siblings were playing, they gave her a controller, and she learned how to play at least so far as she was entertained by it.

I used to be annoyed when she'd play Smash on my team and constantly kill herself to be amused by the fountain of light and death shouts and how she'd seek out bob-ombs and kick them because the explosion was funny. And, really, that's no different from me beating up my P2 in Battletoads back in the day.

Nowadays she plays to win, same as I did as a teenager.

I honestly wouldn't give too much thought to the hardware being extra accessible. She started with an N64, and that controller's a puzzle in itself. You just want to make sure to buy beginner games because your brother is, in fact, a beginner. He's autistic but mostly he's just a kid.