Ethel Kennedy knew husband Robert was a serial cheat who had affairs with actresses Kim Novak and Lee Remick - AND sister-in-law Jackie

Ethel Kennedy, who died Thursday aged 96, lived a life filled with tragedy made painful by her knowledge of her husband's many affairs.

But she put up with Bobby's cheating because she knew from the outset that  there was 'no tradition of monogamy in the Kennedy clan'.

Bobby's widow understood the Kennedys better than anyone who wasn't born into the family and was fully aware of what she was getting herself into.

She knew that infidelity was the price to pay for being married to a Kennedy man and that she had to keep her mouth shut under an unspoken contract.

Ethel even turned a blind eye too the rumors that her husband was sleeping with his sister-in-law Jackie Kennedy.

She admitted that the close friendship between the two may not have been entirely bad for her husband and that it may have been Jackie who finally lifted Bobby from his deep despair after Jack's 1963 assassination. 

The details of  Ethel's unwavering support for her husband were best outlined in the 2016 book 'Bobby Kennedy: The Making of A Liberal Icon' by Larry Tye.

The book said Ethel loved her husband 'more completely than she dreamed possible' – and this meant she was able to look the other way.

Bobby was seen as the most puritanical of his eight siblings and he was the one who was asked to be Attorney General by his brother when he became President.

Bobby's tough, bare knuckle political style was just like their wealthy father Joseph Kennedy

And according to Tye, he also learned his wandering eye from his father as Joe had a mistress, silent film star Gloria Swanson, and flings with numerous other women.

Tye wrote that Joe passed down to his sons the idea that 'when it came so sexual mores, boys play while girls pray'.

Bobby's first sexual experience was at a whorehouse in Harlem, New York, at 21 after his father paid for him to have sex with a black woman – Bobby's verdict afterwards was that it 'wasn't bad, but it wasn't fabulous either'.

He married Ethel in 1950 when she was 22 and the following year Kathleen, the first of their 11 children was born. The youngest, Rory wasn't born when her father was gunned down in a Los Angeles hotel.

But outside of his marriage Bobby's list of conquests supposedly included stars including Kim Novak, Lee Remick and the singer Claudine Longet.

He supposedly was having an affair with Marilyn Monroe too – possibly at the same time as his brother.

Tye interviewed Ethel, then in her late 80s, extensively for the book and gave one of the frankest accounts so far of her late husband's dalliances.

The book said: 'Ethel has lived with the rumors for fifty years and she says she long ago stopped listening to or reading them.

'She tried to block them out then too, although they must have hurt.

'She never disclosed any suspicions.

'She also understood Bobby's family better than anyone else who wasn't born into it, and she knew what whatever her church and theirs said about sex outside marriage, there was no tradition of monogamy in the Kennedy clan.

'She loved her husband more completely than she dreamed possible and still does.

'And she knew he always came home, not just to the kids but her'.

Richard Goodwin, a friend of Bobby's who traveled with him extensively, was more blunt and said that it was a 'Kennedy family tradition' to sleep around, though Bobby was 'much more selective and limited' than his brother Jack.

FBI files claimed that Bobby and Jackie, who died in 1994, were sleeping together from 1964 until he was assassinated in 1968.

Their relationship was said to be based on their shared grief and on a long-standing affection between the two.

According to Tye, the night of Jack's funeral Bobby asked her: 'Shall we go visit our friend' and the two got down on their knees in silent prayer at his headstone.

Tye writes: 'They had been close friends before, but not intimate confidants like this.

'While Ethel had always had issues with Jackie, until now they hadn't included jealousy'.

FBI files revealed that Ethel was so concerned about the alleged affair that at one point she confronted David Ormsby-Gore, British ambassador to the United States during the Kennedy administration, and asked what, if anything, he knew about the relationship.

But what is clear is that they were both 'devastated by their loss and each was determined to help the other through'.

When JFK was shot, Bobby made a point of going  to Andrews Air Force Base to meet Jackie and his brother's body.

Even though the entire nation was in mourning 'nobody, not even Jackie, would grieve as "deeply or as long as Bobby did",' Tye wrote.

The book said: 'The two were closer than any brothers had been at high levels of government, talking in a private code, perpetually interrupting each other and finishing each other's sentences.

'Gone now were the dreams of what they could accomplish side by side..

'The sniper's bullet that had penetrated Jack's skull shattered Bobby's own vision even as it broke his heart'.

Bobby's assassination wass just one of a whole slew of tragedies that struck Ethel during her life.

Her parents were killed in a plane crash in 1955, and her brother George, died in the same way 10 years later., two months before his widow choked to death.

Two of her sons predeceased her, David succumbing to a drug overdose in 1984 and Michael in a skiing accident on New Year's Eve 1997.

Scandal too surrounded her family. Son Joe had a car accident in which a passenger was paralyzed. Bobby Jr. – who has split with most of the family over his support for Donald Trump – was arrested for heroin possession and before his death Michael went into sex addiction therapy in Maryland after it was discovered he was having an affair with his babysitter that started when she was just 14.