At the age of 64, Jackie Kennedy was diagnosed with non-Hodgkin's lymphoma that mostly affected her neck, chest, and abdomen. At first, her prognosis was good, and the former first lady started treatment immediately. However, her health rapidly declined, and she passed away a short while later. "Jacqueline Kennedy Onassis was a model of courage and dignity for all Americans and all the world. Even in the face of impossible tragedy, she carried the grief of her family and our entire nation with a calm power that somehow reassured all of us who mourned," President Bill Clinton said after her passing, as per The Washington Post.

In the biography titled "Jackie: Public, Private, Secret," author J. Randy Taraborrelli shared Jackie's last moments with her former lover, architect Jack Warnecke. According to People, the pair had a three-year relationship shortly after John F. Kennedy's assassination, but they never took it to the next level despite Warnecke's wishes.

When Jackie was battling cancer, she called Warnecke. He revealed to Taraborrelli that she thought she had beaten the illness, as well as that she never got over JFK's death. "I got past it, maybe, but never over it," Jackie told Warnecke. The former lovers burned some of Jackie's old letters in the fireplace of her Fifth Avenue home, including notes from both of her late husbands. Jackie succumbed to cancer two months later.