Los Angeles: "The Godfather" actor Gianni Russo says he lost his virginity to Hollywood star Marilyn Monroe when he was 15 and she was 33.
Russo claims the pair maintained a close relationship up until her death aged 36 in 1962.
"Marlon Brando was my only acting teacher, Frank Sinatra was my only singing teacher and Marilyn Monroe made me a man," the 75-year-old told thesun.co.uk.
"She taught me everything I know. I thought I was the luckiest boy alive but if it had happened today, I think she'd be arrested and my parents would have tried to get some cash out of it.
"Was I upset? No. I'd just had sex with America's hottest movie star and sex symbol."
In his memoir "Hollywood Godfather: My Life In The Mob And Movies", Russo shares how he met the actress when he was working at a hair salon in New York.
"She came in often and always asked for me to shampoo her hair," he explained in the book.
"Marilyn was very friendly. After a few visits I got over the movie star hype and saw her as a normal person, albeit one with a dynamite body."
Shortly after, Russo says one of her advisors invited him to the Waldorf Hotel, where she was staying.
"I figured she was going out and needed me to help her with her hair," he continues.
"Marilyn was alone in a lavish suite replete with an outdoor terrace, but the entire place looked like the set of a disaster movie.
Clothes thrown everywhere, dirty dishes on the sofa. The bed unmade and she looked like a homeless waif without make-up.
"She was wrapped in a white towel and had a flute of champagne."
Monroe offered him a glass before she dropped her towel and invited him to join her in her bath.
"My heart was pounding," he recalls. "Like an idiot, I covered my eyes, which made her laugh.
"I began undressing, praying I wouldn't trip over my pants and fall on my a**, and then entered the tub. I'll be honest, I had no idea what to do, or what she expected.
"We wound up in bed for the entire weekend, climbing out only when needed. It was my first experience of room service, and it added to the fantastic experience."
Russo tells how he came crashing back to reality when he returned to work on Monday morning.
He continues: "I didn't tell anyone, not just because I was a gentleman, but who would believe me?"
Russo tells how he continued to sleep with her but kept it secret.
It was not until several years later when he was working on the pre-production of "The Godfather" that he opened up about their relationship.
He recalls: "Marlon Brando, who was one of her many lovers, was talking about her and lamenting her early death. Marlon said wistfully, 'She oozed sex. Man, she was great'."
Unconsciously, Russo nodded in agreement and Brando asked him: "Did you bed her?"
Brando asked him to prove it by revealing something intimate about her body. Russo says: "I jabbed my upper right thigh and said, 'Scar, right about here.'
"I told him that I was almost 16 and it went on for a while. Marilyn was 33 at the time. Afterwards, I felt bad telling him about it."