Fifty years after her death, an author who met the star has questioned her sexual identity.
Although she married and divorced three times, she was - though few people are aware of the fact - a lesbian by inclination.
She admitted to sexual encounters with actresses Joan Crawford, Barbara Stanwyck, Marlene Dietrich and Elizabeth Taylor, as well as with both her acting coaches, Natasha Lytess and Paula Strasberg.
Only a day before Jean Negulesco, who directed her in 'How To Marry A Millionaire', was due to visit her, Monroe was found dead.
"I still think I might have saved her if I could have got to her in time," the Daily Mail quoted him as saying.
"You know what was wrong with her, don't you?
"Her whole existence was a search for identity, and her sexual identity was a complete lie.
"She told me once she had never had an orgasm with a man in her entire life," he said.
Another of those who worked with Monroe, actress Celeste Holm, who appeared with her in 'All About Eve', and who died last Sunday, said that Marilyn's sexual problems were rooted in her traumatic childhood.
Born illegitimately in 1926 to an unmarried mother in the charity ward of the Los Angeles General Hospital, she was originally known as Norma Jeane Mortenson, the child of a 24-year-old film negative cutter, Gladys Pearl Monroe Mortenson, who developed schizophrenia.
Both of Gladys's parents, Otis Elmer Monroe and Della Monroe Grainger, lived out their twilight years in mental institutions, while Gladys's brother, Marion, was diagnosed with paranoid schizophrenia.
So it is small wonder that the child who became Marilyn Monroe grew up with a deep-rooted fear of genetic insanity.
This, according to Celeste Holm, gave Marilyn a lifelong terror of pregnancy.
In addition to her fear of giving birth to an abnormal child, Marilyn suffered from devastating bouts of endometriosis, a gynaecological condition causing intense pelvic pain, severe cramps and painful periods.
It made normal sexual intercourse difficult and uncomfortable.
"Because of this Marilyn was never able to enjoy sex with men," Holm said.
"She was afraid of it, and turned to older women as sexual role models," she had said.
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