The 47-year-old journalist told host David Letterman his mother "hooked up" with stars such as Frank Sinatra and Marlon Brando. Cooper is the son of Vanderbilt and Wyatt Emory Cooper, and the conversation started after he denied Sinatra is his father.
"Although, my mom actually dated Frank Sinatra," he acknowledged. "My mom, who's now 90... she wrote this book all about the guys she hooked up with."
Vanderbilt was born the only child of railroad heir Reginald Claypoole Vanderbilt in 1924, and married her first husband, Pat DiCicco, in 1941. The couple divorced in 1945, and the heiress went on to marry Leopold Stokowski, Sidney Lumet and Cooper. She was involved with many other celebrities over the years, and detailed her love affairs in It Seemed Important at the Time: A Romance Memoir.
"My mom has no filter," Cooper related. "We were watching a movie when I was a kid -- I remember watching On the Waterfront with her, and I was like, 'Do you know Marlon Brando?' And she'd be like, 'Oh, yes.'"
"It turns out my mom and Carol Matthau, who become Walter Matthau's wife... both saw On the Waterfront or A Streetcar Named Desire together, and they both decided they wanted to hook up with Brando," he continued. "Carol was the first one to do it, and then she set it up for my mom."