From American royalty to Polish royalty, these sisters were stars.

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It’s hard to imagine a more iconic sister act than Jacqueline Kennedy and her sister Lee. Born three years apart, the sisters captured the American imagination with their incredibly glamorous lives and their ability to elegantly soldier through tragedy. As children, the sisters were very close, attending school at Miss Porter’s, horseback riding, and running through the halls of New York City penthouses, their Hamptons summer house, their step-father’s incredible Virginia mansion Merrywood, and their Newport, Rhode Island vacation homes. They went on a sisters-only trip to Europe when Jackie was 21 and Lee 18 making headlines everywhere they went as two stylish, aristocratic Americans abroad.

But as anyone with a sister knows, sibling rivalry can be very real. When Jackie’s husband became the President of the United States, her public life started to overshadow her sister’s. Lee, however, had an enviable jet-setting life filled with high fashion, good fun, and celebrities eager to be around the elegant, intelligent, and engaging woman, regardless of who her sister happened to be.

Here are a dozen things you may not know about Lee Radziwill’s incredibly glamorous life:

1. Her full name is Caroline Lee Bouvier, but she was called Lee after her maternal grandfather James Lee a successful real estate mogul and banker

2. She beat Jackie to the altar, marrying book-publishing scion Michael Temple Canfield, on April 18, 1953, who she had known and dated since she was 15. The wedding reception was held at Jackie’s and Lee’s childhood home, Merrywood. (Not to be upstaged by her little sister, soon after, Jackie got engaged to the most eligible bachelor in America—the young senator John F. Kennedy)

3. Lee later married Prince Stanislaw “Stas” Radziwill of Poland, which gave her the title Princess Lee Radziwill. The couple had two children Christina and Anthony, who was a close friend of Jackie’s son, John F. Kennedy Jr.

4. Their son Anthony’s wife Carole Radziwill starred on The Real Housewives of New York.

5. While Jackie was known as the First Lady of Style, for years Lee served as her de facto stylist, helping her find just the right look for state dinners and official outings.

6. Author Truman Capote was a big fan of Lee, saying: “I can’t think of any woman more feminine than Lee Radziwill—not even Audrey Hepburn.”

7. At Capote’s suggestion, she appeared in an off-Broadway production of The Philadelphia Story. She was a natural as the refined Tracy Lord, played by Katherine Hepburn in the film version. Yves Saint Laurent was brought in to design all of her costumes.

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8. Lee dated Greek shipping magnate Aristotle Onassis years before he became Jackie’s second husband.

9. Lee was part of artist Andy Warhol’s artsy New York circle, even appearing on the cover of his magazine, Interview

10. According to Vanity Fair, she once hosted Mick Jagger at her house in Montauk, New York.

11.She wanted to host her own talk show, Conversations with Lee Radziwill, where she chatted with some of her famous friends, including Gloria Steinem and fashion designer Halston.

12. Lee married the filmmaker Herbert Ross, the man who brought us both Footloose and Steel Magnolias