ROBERT DUVALL, actor

I would like to jump on the band wagon and see if anyone can help with this person.I too have stories in my family of Robert Duvall being a relative.My great grandfather's name is Edward Duvall and we can find no information on him except the rumor that Edward's father and Robert Duvall's father were brothers.Is there a good biography out there on Robert Duvall that may give some family background.I am more interested in finding out about my great grandfather then Robert Duvall but thought because he is a star that maybe someone has done some research on him and has some helpful information.

An aside - We have a picture of my great grandfather (Edward Duvall) and he and Robert could be twins they look so much alike.

Thank You
Lisa Kent