My girls adore their brother. They love to play with him and can get really excited when playing with him. He loves them and gets a kick out of them. He does, however, get overwhelmed by their enthusiasm.
They get so loud, so energetic, and so overwhelming that after a while he will let me know he wants to go to bed alone "for a nap". In reality, his little autistic heart just needs a little time in the peace of his room. (Where he can get loud on his own terms.)