Lyric discussion by EmptyPromise 

Cover art for Spaceboy lyrics by Smashing Pumpkins, The

For those who said this song was about and for Billy's brother is correct. Now, in response to what y2doggy asks about the line "we won't belong," I remember reading somewhere that as children and as adolescents, Billy considered both himself and his brother as outcasts. Billy didn't belong because he was emotionally different from other children (i.e. he was always sad, etc) and his brother didn't belong for the obvious physical characteristics of his disease/illness.

That's exactly what I was thinking when I heard those lines. This song makes me tear up.