Monroe was found dead from an accidental overdose in August 1962, however it’s being alleged that the singer and actor believed her death was associated with her high-profile affairs with John F Kennedy and his brother, Robert.
In a new memoir, titled Sinatra and Me: In The Wee Small Hours, Sinatra’s former manager and close friend, Tony Oppedisano, writes: “Frank believed she was murdered, and he never got over it.”
Oppedisano claims that Monroe, the star of films including Some Like It Hot and The Misfits, often confided in Sinatra, with whom she was close.
After her affairs with the Kennedy brothers ended, and she was ostracised by them, Monroe allegedly told Sinatra “she didn’t understand why they’d shut her out completely once she stopped having sex with them”.
Shortly before her death, Monroe was staying at the Cal Neva Lodge near Lake Tahoe – which Sinatra part owned – and the book says that she was actually there with her ex-husband, the baseball star Joe DiMaggio.
While there, a press conference was announced that Monroe was due to be present at, but she died before it could take place. The book claims the actor was set to announce her reunion with DiMaggio.
However, many believed she would share secrets about her affairs with the Kennedys, and the book claims that Sinatra thought she was silenced because of this assumption.
Oppedisano writes: “Frank believed if the press conference hadn’t been announced, she would have lived a lot longer.”
It’s also claimed that Sinatra “never” thought she’d share secrets of the affairs as she “still had feelings” for John.
The book, which is excerpted in People, alleges that several sources told Sinatra that “she’d been murdered with a Nembutal suppository” and that “Robert Kennedy or the mob was involved”.
Monroe was 36 at the time of her death. Sinatra died from a heart attack in 1998, aged 82.