He used his father to make the music which was outstanding, his sister Talia Shire to play connie, and she was also great. His daughter was a last minute replacement, and as I have said a billion times she wasnt all that horrible.
I agree Hamilton was miscast, but I think Coppola for whatever reason put B list actors in bit parts. The guy who played Merle was some 50's pretty boy whose stage mane escapes me (his real name was Merle. Anyone know who I am talking about?
His name was Troy Donahue although his real name is Merle Johnson.