This story is poignant and tragically sad.
While I was growing up, my parent's had good friends with a severely mentally disabled son. They loved and cherished him, keeping him with them and finding enrichment programs for him no matter where they lived or how old he got.
He was born in 1953 and is still alive. Both of his parents are now deceased and he lives with his older sister.
It isn't easy love but love nonetheless.
Seems like your brother was deeply affected by how he was treated. which is why your story is heartbreaking. The man I describe above doesn't have the capacity for being so deeply affected. He cannot self reflect--he lives inside of each moment.
He's never danced.