Both JFK and Bobby Kennedy are known to have carried on simultaneous affairs with Marilyn Monroe.
But in her new book, the veteran actress Shirley MacLaine has revealed the two brothers were even closer than previously thought - leading the blonde beauty into the same bed, one after another, on the same night.
The night in question just happened to be Jack’s birthday - after Monroe had serenaded him with her infamous rendition of Happy Birthday, Mr President.
In her newly released coffee table book, The Wall of Life, MacLaine, 90, writes: ‘In 1962, at the famous celebration for John F Kennedy’s 45th birthday at Madison Square Garden, Jimmy Durante and I performed for the president and the crowd, but what most people remember is Marilyn Monroe singing “Happy Birthday” to him.
‘Afterward there was a private party at Arthur Krim’s home…
Jack Kennedy had just walked out of the bedroom... and Bobby Kennedy had just walked in. Marilyn was in the bedroom…’
Arthur Krim was finance chairman for the Democratic Party at the time.
In the caption to a black and white photograph, in which both she and JFK are in the background, she writes: Jack Kennedy had just walked out of the bedroom behind me, and Bobby Kennedy had just walked in.
‘Marilyn was in the bedroom…’
MacLaine also implies this wasn’t the first time the ‘revolving door’ into Marilyn’s bedroom took place.
In a later photograph, from 1984, she writes: ‘Here I’m telling Teddy Kennedy that story… and he’s laughing about how the boys got away with it all the time.’
In her best-selling book Ask Not: The Kennedys and the Women They Destroyed, Dailymail.com columnist Maureen Callahan described the crossover relationships between JFK and his brother as an incestuous sexual competition between the two.
In fact, she reveals that, just 30 minutes before Marilyn appeared on stage to sing Happy Birthday, she had sex with Bobby in her dressing room.
They spent 15 minutes alone together, Callahan writes.
The liaison made her late to the stage, where she arrived drunk and flush with the transgressive sex shed just had with Bobby, her dress so tight she could hardly walk.
Both John (right) and Robert (left) chat with Marilyn on the night of her infamous performance
Marilyn had simultaneous affairs with both Kennedy brothers
Jack Kennedy had just walked out of the bedroom behind me, and Bobby Kennedy had just walked in, writes MacLaine. Marilyn was in the bedroom
Jackie Kennedy was furious after the performance, which left JFK slack-jawed in the audience. And so, Callahan writes, Jackie gave her husband an ultimatum, telling him he could no longer see Marilyn, or else she would divorce him — taking the children and costing him a second term.
JFK agreed and never slept with Marilyn again.
However, according to MacLaine, he made that promise after one last bedroom encounter, before handing the tortured actress over to his brother.
According to Callahan, the affair with Bobby continued - with Bobby even visiting her the night she died at her home in LA, on August 4, 1962.
The FBI and the CIA, Bobby and Jack discovered, had bugged Marilyns house and phone line without her knowledge... Bobby wasnt leaving without the tape recordings, she writes.
Where the f*** is it? Bobby demanded. But Marilyn had no idea what he was talking about.
Bobby left empty-handed and Marilyns body was found early the next morning by her housekeeper. She was face-down on her bed, nude, with her phone still in her hand, Callahan writes.
The Marilyn revelation is not the only surprising tit-bit to emerge from MacLaines book of Hollywood memories
She also recalls the moment she managed to escape Donald Trump after a scary interaction with the former President.
Back in probably the 1980s, I interacted with Donald Trump, she writes. I was at some function, and when he walked in, he saw me and straightened up.
He started pulling at his tie, and I could tell immediately that in his mind he was starting to take off my clothes... and his.
MacLaines onscreen chemistry with Jack Nicholson was electric, but she said hed make her laugh too much to be her real-life lover
John, Robert and Teddy Kennedy. Kennedy jokes later that the boys got away with that all the time
It was scary just how obvious he was being. He even figured out a way to try to stop me from leaving, but I had to get out of there.
The Oscar-winning actress also reveals why she and her Terms of Endearment leading man Jack Nicholson never got together, despite their on-screen chemistry
He just made me laugh all the time. He was one of my favorite people. she says.
I dont think he wouldve been my type to have an affair with anyway. I would laugh too much.
And she discloses that - in a romantic history that included affairs with Robert Mitchum, Danny Kaye and Yves Montand - there was one iconic actor who remained immune to her charms.
Under a photograph of herself with Morgan Freeman, she writes tantalizingly: I propositioned him and he turned me down.
Shirley MacLaine had an open marriage with producer and alleged spy Steve Parker for 28 years - who she described as the love of her life.
The Wall of Life: Pictures and Stories from This Marvelous Lifetime by Shirley MacLaine is published by Crown