Jackie Onassis hated Madonna.

In a new book ‘The Good Son: JFK Jr. and the Mother He Loved,’ author Christopher Andersen tells something about the relationship between Madonna and John F Kennedy Jr., and he speaks also about the hate JFK Jr’s mother, Jackie Onassis, proved for Madonna because she posed as Marilyn Monroe.
Here’s an extract of the DailyMail article:

JFK Jr, who was once dubbed the sexiest man alive, reportedly began seeing the Material Girl star in 1988 following the breakdown of her marriage to actor Sean Penn.
In his new book the author tells how Madonna ‘went after’ JFK Jr, telling friends she believed an affair with him ‘would be nothing less than “cosmic”‘.
The book also quotes dancer Erika Belle, one of Madonna’s closest friends at the time, who claims JFK Jr was equally keen.
She said: ‘You could see it in his eyes that first time they met.
‘John was totally in awe.’

JFK Jr and Madonna would reportedly meet at a health club where they shared the same trainer and would occasionally jog around Central Park together in the early morning.
While they managed to keep their relationship secret from the media, JFK Jr was not said to have been shy about introducing the singer to his mother.
The book tells how he brought her to his mother’s Central Park flat where she signed the guestbook ‘Mrs. Sean Penn’, as she was still legally married at the time.

Jackie was reportedly unimpressed with the singer partly due to her use of crucifixes and other Catholic images which had been deemed sacrilegious by the Vatican.
But what is said to have upset her most of all was seeing a copy of Life Magazine which featured Madonna on the cover dressed up as Marilyn Monroe – Monroe being one of several women who her husband had famously cheated on her with.

Author Christopher Andersen writes: ‘One unwelcome reminder of JFK’s torrid affair with Marilyn — the affair that most troubled Jackie — arrived on her doorstep in the form of another blond bombshell by the name of Madonna.’
Another part of the excerpt published highlights the steamy nature of their alleged affair.
It reads: ‘One day while he was staying with Billy Noonan in Hyannis Port, John phoned New York to check his messages.
‘On the other end, a woman with a familiar voice was calling from Rome. “Kennedy,” she began, “I’m drunk and when I see you next I’m going to take your …” The rest was decidedly X-rated, and after John played it for Noonan, his friend asked to hear it again.
‘Unable to quite place the voice, Noonan begged John to tell him who it was. “Madonna,” John answered matter-of-factly.
‘Noonan was speechless. “You are banging Madonna?” Noonan asked. “How do I not know this until now?”
‘So what was it like sleeping with Madonna? “Let me tell you,” Kennedy replied, “she’s a sexual dynamo.”’
The book tells how at the time JFK Jr was still dating steady girlfriend Christina Haag – who Jackie O wanted him to marry – but somehow managed to keep his relationship with Madonna secret from her.

However Madonna’s ex husband Sean Penn is said to have confronted JFK Junior over it when they met at a party in Robert De Niro’s honor at the Tribeca Grill.
When JFK junior went to intorduce himself, Mr Penn, reported snarled: ‘I know who you are. You owe me an apology.’
According to the book JFK Jr then ‘beat a hasty retreat’ because he was aware of Penn’s reputation for fighting.
JFK Jr is known to have had relationships with a string of women including Sex and the City actor Sarah Jessica Parker, who he is said to have seen at the same time as Madonna.
He died in 1999 in a plane crash along with his wife Carolyn Bessette, and her elder sister Lauren.