Yes the song was written about Brian Wilson, by Bruce Johnston, who was able to tour with the Beach Boys because with Wilson's ongoing drug problem he sometimes refused to tour. Johnston wrote many of the Beach Boys songs. David Cassidy was actually the first person to record the song, though it was not released, but when Clive Davis heard the Cassidy version, he had Manilow record it. Incidentally, the song won a Grammy for Song of the Year, and it was the only Grammy that any Beach Boy won.