Why Jackie O Never Confronted Her Husband Aristotle Onassis About His Affair With Maria Callas

"Jackie was not happy.”

Following the death of President John F. Kennedy, widow Jackie Kennedy remarried Greek businessman Aristotle Onassis in 1968, and while Kennedy stayed with the tycoon until his death in 1975, there were reportedly three people in their relationship.

According to his longtime secretary, confidant, and friend, Kiki Feroudi Moutsatsos, Onassis had a decade-plus-long affair with famous opera singer Maria Callas. The performer and businessman were so close, in fact, Onassis “couldn’t live without Maria,” Moutsatsos told People in a new interview. The longtime lovers first met in 1957, and at the time, were both in previous marriages: Callas to Giovanni Meneghin and Onassis to his first wife Athina Livanos.

After they began seeing each other, they never stopped, Moutsatsos said. Not even when Onassis and Kennedy tied the knot. “Maria was a piece of his soul, of his body, of his brain,” she continued. “That’s why they never believed that they could be separate.”

Kennedy was aware of the Greek tycoon and opera singer's relationship, and while she "was not happy," she never brought up Callas. “Jackie was never screaming, never fighting,” Moutsatsos remembered. “Although she knew many things from Aristo’s behavior, but she was pretending that nothing happened. She was very smart.”

She did, however, disclose her feelings to Onassis's sister, Artemis Garofallidou, who told Kennedy "not to fight him." Kennedy stayed mum about the affair, only occasionally calling out Onassis's behavior.

“But Jackie was not happy,” Moutsatsos continued. “She had melancholy. She never spoke [directly] about Maria Callas. What she spoke of was Onassis's behavior. If I could characterize her, I would say that she was behaving like a cat. Very smart. Very clever. She would wait for the right moment to speak with him about his behavior.”

Kennedy initially married the man who was 23 years her senior so she "wouldn’t have to worry about money and the physical security of her children," professor of U.S. gender and women’s history at Ohio University Katherine Jellison told Time. “There was a fondness, and I think, respect between Jackie and Aristotle Onassis. It was not a great love story.”

Callas, on the other hand, was not as complacent. The singer was quite "mad" about his marriage to Kennedy and had "many things" to say on the matter. "Of course she was mad—and she was also very proud," Moutsatsos recalled. "I remember once she said, ‘I don’t want to be compared with this woman.’"

While Moutsatsos said Onassis was "proud" of his marriage to Kennedy (“He had succeeded in getting married and having next to him the First Lady of the United States.”), she believed that Onassis and Callas were meant to be together. “They [Callas and Onassis] were born for each other," she explained.

Aristotle Onassis died of respiratory failure from complications of myasthenia gravis on March 15, 1975, which devastated Callas. According to Moutsatsos, the opera singer “lost her appetite to live. She didn’t want to eat. She didn’t want to go out. She didn’t want to speak with friends.” She retreated from her life in the spotlight and died just two years later from a heart attack.

The story of Onassis and Callas will be documented in the upcoming Pablo Larraín directed film Maria starring Angelina Jolie. While Larraín said "very extensive research” went into making the movie, he told Deadline that it isn't a "proper biopic."

"That is an invention from culture," said Larraín, who also directed the 2016 film Jackie. "I don’t think a movie can actually capture anyone in reality unless that person is in front of you talking to you.”

Moutsatsos, who published a memoir that recounts the love story titled The Onassis Women, added that she is the only person still alive who knows the truth. “I’m the only one who remembers,” she said. “In my book is the real truth.”

Moutsatsos also worked with producers Jack Monderer and Beth Tribolet and director Heidi Lauren Duke to develop a short film titled, The Heiress. Larraín and Jolie's Maria is currently in select theaters and will be available for streaming on Netflix on December 11.