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By Kalhan Rosenblatt and The Associated Press

Lee Radziwill, the glamorous younger sister of former first lady Jacqueline Lee Kennedy, spent her life as a stylish jet setter and socialite. Radziwill died of natural causes in Manhattan on Friday at the age of 85, the Associated Press reported Sunday.

"We are heartbroken and I will miss our dear friend. Rest In Peace, Lee Radziwill," fashion designer Tory Burch tweeted a day earlier.

Radziwill was born Caroline Lee Bouvier to Janet Norton Lee and John "Black Jack" Bouvier on March 3, 1933. She attended Miss Porter's School and Sarah Lawrence College, and was introduced to society in 1950. The husky-voiced Radziwill shared her older sister's affinity for fashion and globe-trotting, as well as her dark, wide-set eyes and high cheekbones.

First Lady Jacqueline Kennedy stands with her sister, Princess Lee Radziwill of Poland, and niece, Anna Christina Radziwill, on the walkway outside the Oval Office with the Kennedy family dog Clipper at the White House on January 15, 1963. Cecil Stoughton / JFK Library via Reuters file

Radziwill was extremely close to Kennedy Onassis, and visited the White House often prior to President John F. Kennedy's assassination. She was with the president when he made a trip to London in 1961, and Kennedy was godfather to Radziwill's daughter, Anna Christina.

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The wardrobe for Kennedy Onassis' trip to Paris in 1961, which would become a signature moment for the first lady, was selected by Radziwill.

Her widely admired fashion sense earned her an induction to the 1996 International Best Dressed Hall of Fame, according to Vanity Fair.

Although she was iconic herself, Radziwill's inner circle were equally elite, including artist Andy Warhol, writer Truman Capote, and ballet dancer Rudfolf Nureyev.

She also worked in a host of roles at Giorgio Armani, including as a brand ambassador and public relations executive, Vanity Fair reported. Radziwill also dabbled in acting and interior design.

Radziwill began work on a film with collage artist and photographer Peter Beard about her childhood in East Hampton, New York. But after a few creative evolutions, and the introduction of filmmakers Albert and David Maysles, it became "Grey Gardens," the classic documentary about her eccentric aunt and cousin.

Edith Bouvier Beale and her eponymous daughter were immortalized in the 1975 film, later a Broadway musical and Emmy-winning HBO movie.

Although her life was filled with adventure and glamour, it was also marked by tragedy. Her son, Anthony Radziwill, died at age 40 of cancer on Aug. 10, 1999 — less than a month after the death of nephew, John F. Kennedy Jr.

Radziwill was married three times. First, in 1953 to Michael Canfield, a publishing executive. The couple later moved to England for several years before their marriage was annulled.

In 1959, Radziwill married Polish aristocrat Prince Stanislaw Albrecht Radziwill. After their marriage, Radziwill's title became "Her Serene Highness," according to W Magazine. The couple had two children and were divorced in 1974.

Radziwill would marry for a third time to filmmaker Herbert Ross, but again divorced in 2001. Following her third divorce, Radziwill went back to using the last name from her second marriage, which was the same last name as her children.