Anderson Cooper Felt ‘Awkward’ Discussing Mom Gloria Vanderbilt’s Hot Dates (Video)

Sundance 2016: HBO docu details the times heiress spent with Howard Hughes, Marlon Brando, Frank Sinatra and Errol Flynn — when she was 17

CNN anchor Anderson Cooper was the one who felt awkward, not his famous mother Gloria Vanderbilt, when they talked about her romantic past, he told TheWrap.

Vanderbilt dated Howard Hughes, Marlon Brando, Roald Dahl and Frank Sinatra, and the discussions informed a book they wrote together, “The Rainbow Comes and Goes.” It’s creation is chronicled in the HBO documentary “Nothing Left Unsaid: Gloria Vanderbilt & Anderson Cooper.”

It premiered Saturday at the Sundance Film Festival in Park City, Utah, and the newsman and the film’s director, Liz Garbus, sat down with TheWrap’s Matt Donnelly. They talked about her dating Hollywood heavyweights and her marriages to producer Pat DiCicco, conductor Leopold Stokowski, director Sidney Lumet and author Wyatt Cooper.

Vanderbilt had no problem with dishing on relationships, including one with Errol Flynn, when he was 32 and she was 17. But Cooper said he did.

“There were things she was talking about and I was like, ‘Mom, I really don’t need to hear about your dating life,'” he said. He also discussed the painful losses he and mother felt when his father died, and his brother committed suicide, as well as growing up as the son of an heir to the Vanderbilt fortune.

The book arrives on April 5, just days before the documentary will be on HBO.