How Jackie Kennedy Discovered She Shared a Therapist with JFK’s Rumored Mistress Marilyn Monroe (Exclusive)

According to a new book, the former first lady confronted her therapist about previously having treated her husband's rumored mistress

The relationship between Marilyn Monroe and John F. Kennedy is now the stuff of legend— but for Jacqueline Kennedy Onassis, the affair was almost inescapable. So much so that in the 1970s, the former first lady was shocked to discover her therapist had once treated Monroe.

According to a new biography — Jackie: Public, Private, Secret by J. Randy Taraborrelli, exclusively excerpted in this week's issue of PEOPLE — Jackie entered therapy with psychoanalyst Dr. Marianne Kris in the early seventies, midway through a turbulent marriage to Greek shipping magnate Aristotle Onassis.

Related: Why Jackie Kennedy Quietly Burned Personal Letters and Photos Before She Died (Exclusive Book Excerpt)

Patricia Atwood, Kris’ secretary from 1972 to 1974, told Taraborrelli in an email, “Dr. Kris would never discuss Mrs. Onassis, citing doctor-patient confidentiality."

But in notes, the therapist detailed some of her sessions with Jackie.

"They addressed Mrs. Onassis’s ongoing PTSD over the assassination, as well as certain nagging issues about their marriage. He went out in a blaze of glory, Mrs. Onassis said, according to one of the notes I read," Atwood shared. "The way he died had completely robbed her of the right to hate him, she said. Next to that entry, Dr. Kris wrote that her grief was anything but, as she put it, ‘tidy.’"

At one point, Jackie was informed that Dr. Kris had once treated Monroe — long believed to have had an affair with her first husband, JFK, one of his many infidelities.

Writes Taraborrelli: "When Jackie confronted her, [Dr.] Kris said she felt no responsibility to inform her about any former patients in the same way she’d never reveal that she’d ever treated Jackie. Marianne asked, 'How is this relevant?' to which Jackie responded, 'How is that not relevant?'"

Related: PEOPLE Explains: All About Marilyn Monroe's Alleged Affairs with JFK and Brother Bobby

Rumors about Monroe's alleged affair with JFK were spurred in part by her sultry "Happy Birthday" performance for the commander-in-chief at his 45th birthday celebration at Madison Square Garden on May 19, 1962, just months before the film star's death.

In the years that followed, accounts of Monroe's affairs with both the late president and his brother, the late Sen. Robert F. Kennedy, have been explored in countless news reports, books and interviews.

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer.

Monroe biographer Jason Spada told PEOPLE in 2012 that President Kennedy had essentially passed off the actress to his brother after he grew tired of the romance — although "it was pretty clear that Marilyn had had sexual relations with both Bobby and Jack," Spada said at the time.

It's been nearly sixty years since Jackie was by her husband’s side in the Dallas motorcade when he was assassinated on Nov. 22, 1963.

She would go on to marry Onassis in 1968, and in her later years, she found companionship with diamond merchant Maurice Tempelsman.

In early 1994, she was diagnosed with non-Hodgkin lymphoma, and died on May 19 of that year. Until the end, she always remained private about her personal life,

For more People news, make sure to sign up for our newsletter!

Read the original article on People.