Caroline Lee Radziwill reportedly died on Friday in New York City.
She was 85 years old.
Born in 1933 as Caroline Lee Bouvier, Ms Radziwill was an American socialite, PR executive and interior designer.
She was the younger sister of Jackie Kennedy (nee Bouvier) and grew up with her sibling in Southampton, New York with stockbroker parents.
After not succeeding as an actor Radziwill worked as an interior decorator with numerous wealthy clients. She was also a public relations executive for Giorgio Armani.
Radziwill married three times and had two children.
The film Grey Gardens, which was also a successful musical and TV movie was based on the life of Radziwill’s eccentric and reclusive extended family members, Edith Ewing Bouvier Beale (”Big Edie”) and her daughter Edith Bouvier Beale (“Little Edie”).
Radziwill had suffered from age-related disease in recent years, but was still in good health, maintaining her reputation of elegance up until her death, WWD reports.
Radziwill was married three times: first to publishing executive Michael Canfield, then to Polish Prince Stanislas Radziwill, with whom she had two children, and finally to film director Herb Ross.
Radziwill entered in the Best Dressed Hall of Fame in 1994, and was known to hit the town with famous names such as Truman Capote and Andy Warhol.
Lee and her older sister, Jackie were the “it girls” of the 1960s, though Lee admitted that she often felt overshadowed by the former First Lady.
In her biography, she reportedly wrote that their father favoured Jackie over her, writing: “That was very clear to me but I didn’t resent it because I understood he had reason to.”
She is survived by her daughter Anna, and daughter-in-law Carole Radziwill, author and former television personality on the program Real Housewives of New York.
Her son Anthony, Carole’s husband, died of cancer in 1999.