Lee Radziwill (left) and Jacqueline Kennedy.Photo:Sylvain Gaboury/Patrick McMullan via GettyJacqueline Kennedy OnassisandLee Radziwill’ssibling rivalry has made headlines for years, and details of the sisters' dynamic continue to garner attention.As a connoisseur and confidante of the world’s most beautiful, elegant and moneyed women, novelistTruman Capotealways had a reverence for Radziwill, according to Laurence Leamer, author ofCapote’s Women, a book that inspired the current FX seriesFeud: Capote vs. the Swans,about Capote’s adoration for gorgeous women he called his “swans.“In the beginning, the sisters and Capote were all friends, but thatdidn’t last long, Leamer tells PEOPLE.“Truman took [Radziwill’s] side against her sister and she was absurdly jealous of Jackie,” he says. ”He was very, very close to [Kennedy Onassis] until he wasn’t.”Truman Capote and Barbara “Babe” Paley ca. 1957. ; Lee Radziwill and Truman Capote pose for the camera at the Emmy Awards on June 4, 1967.ullstein bild/ullstein bild/Getty ; BettmannWhen the competition between the sisters grew larger than their closeness — around the time Kennedy Onassis’s first husband,John F. Kennedy, was elected president, imparting Kennedy Onassis with the title of First Lady — Leamer says the conflict became worse than ever.“Lee was obsessively jealous of her,” Leamer notes. “She couldn’t get over it, and that was her first conversation with Truman. And it’s a very American thing: you meet somebody and tell them the most intimate details of your life, and when Lee and Truman had lunch the first time, there she is talking about her obsession with Jackie.“Back in 1975 and 1976, chapters of Capote’s work-in-progress,Answered Prayers, were published inEsquire. His writing revealed Radziwill and Kennedy Onassis' most salacious secrets, which resulted in Capote’s excommunication from their social circle.“She hardly knows this guy and what is he doing? He goes out the door, he tells everybody,” Leamer says, later adding, “He talks about how Jackie looked more like a man, which is a pretty insulting thing to say about the president’s widow and how incredible looking Lee was.“Lee Radziwill (left) and Jacqueline Kennedy.Dave Allocca/Starpix/Shutterstock ;GettyAlthough the siblings' feud over what Leamer says was money, men (Radziwill dated Aristotle Onassis before he married Kennedy Onassis in 1968) and status was made public, but the sisters were there for each other behind closed doors when times got tough.When JFK wasassassinatedin 1963, Radziwill,who died in 2019, flew to Washington D.C. from her London home to comfort her sister. When asked about their rivalry in 1976, Radziwilltold PEOPLE, “It’s just the most ludicrous talk in the world. We’re exceptionally close and always have been.”Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.Still, that rivalry always seemed to linger. When Kennedy Onassis died in 1994, her will revealed she would not beleaving any moneyto her younger sister.“I’ve made no provision in this, my will, for my sister, Lee B. Radziwill, for whom I have great affection because I have already done so during my lifetime,” it read.

Lee Radziwill (left) and Jacqueline Kennedy.Photo:Sylvain Gaboury/Patrick McMullan via Getty

Lee Radziwill and Jacqueline Kenned

Sylvain Gaboury/Patrick McMullan via Getty

Jacqueline Kennedy OnassisandLee Radziwill’ssibling rivalry has made headlines for years, and details of the sisters' dynamic continue to garner attention.As a connoisseur and confidante of the world’s most beautiful, elegant and moneyed women, novelistTruman Capotealways had a reverence for Radziwill, according to Laurence Leamer, author ofCapote’s Women, a book that inspired the current FX seriesFeud: Capote vs. the Swans,about Capote’s adoration for gorgeous women he called his “swans.“In the beginning, the sisters and Capote were all friends, but thatdidn’t last long, Leamer tells PEOPLE.“Truman took [Radziwill’s] side against her sister and she was absurdly jealous of Jackie,” he says. ”He was very, very close to [Kennedy Onassis] until he wasn’t.”Truman Capote and Barbara “Babe” Paley ca. 1957. ; Lee Radziwill and Truman Capote pose for the camera at the Emmy Awards on June 4, 1967.ullstein bild/ullstein bild/Getty ; BettmannWhen the competition between the sisters grew larger than their closeness — around the time Kennedy Onassis’s first husband,John F. Kennedy, was elected president, imparting Kennedy Onassis with the title of First Lady — Leamer says the conflict became worse than ever.“Lee was obsessively jealous of her,” Leamer notes. “She couldn’t get over it, and that was her first conversation with Truman. And it’s a very American thing: you meet somebody and tell them the most intimate details of your life, and when Lee and Truman had lunch the first time, there she is talking about her obsession with Jackie.“Back in 1975 and 1976, chapters of Capote’s work-in-progress,Answered Prayers, were published inEsquire. His writing revealed Radziwill and Kennedy Onassis' most salacious secrets, which resulted in Capote’s excommunication from their social circle.“She hardly knows this guy and what is he doing? He goes out the door, he tells everybody,” Leamer says, later adding, “He talks about how Jackie looked more like a man, which is a pretty insulting thing to say about the president’s widow and how incredible looking Lee was.“Lee Radziwill (left) and Jacqueline Kennedy.Dave Allocca/Starpix/Shutterstock ;GettyAlthough the siblings' feud over what Leamer says was money, men (Radziwill dated Aristotle Onassis before he married Kennedy Onassis in 1968) and status was made public, but the sisters were there for each other behind closed doors when times got tough.When JFK wasassassinatedin 1963, Radziwill,who died in 2019, flew to Washington D.C. from her London home to comfort her sister. When asked about their rivalry in 1976, Radziwilltold PEOPLE, “It’s just the most ludicrous talk in the world. We’re exceptionally close and always have been.”Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.Still, that rivalry always seemed to linger. When Kennedy Onassis died in 1994, her will revealed she would not beleaving any moneyto her younger sister.“I’ve made no provision in this, my will, for my sister, Lee B. Radziwill, for whom I have great affection because I have already done so during my lifetime,” it read.

Jacqueline Kennedy OnassisandLee Radziwill’ssibling rivalry has made headlines for years, and details of the sisters' dynamic continue to garner attention.

As a connoisseur and confidante of the world’s most beautiful, elegant and moneyed women, novelistTruman Capotealways had a reverence for Radziwill, according to Laurence Leamer, author ofCapote’s Women, a book that inspired the current FX seriesFeud: Capote vs. the Swans,about Capote’s adoration for gorgeous women he called his “swans.”

In the beginning, the sisters and Capote were all friends, but thatdidn’t last long, Leamer tells PEOPLE.

“Truman took [Radziwill’s] side against her sister and she was absurdly jealous of Jackie,” he says. ”He was very, very close to [Kennedy Onassis] until he wasn’t.”

Truman Capote and Barbara “Babe” Paley ca. 1957. ; Lee Radziwill and Truman Capote pose for the camera at the Emmy Awards on June 4, 1967.ullstein bild/ullstein bild/Getty ; Bettmann

Truman Capote and Barbara “Babe” Paley ca. 1957. ; Lee Radziwill and Truman Capote pose for the camera at the Emmy Awards on June 4, 1967.

ullstein bild/ullstein bild/Getty ; Bettmann

When the competition between the sisters grew larger than their closeness — around the time Kennedy Onassis’s first husband,John F. Kennedy, was elected president, imparting Kennedy Onassis with the title of First Lady — Leamer says the conflict became worse than ever.

“Lee was obsessively jealous of her,” Leamer notes. “She couldn’t get over it, and that was her first conversation with Truman. And it’s a very American thing: you meet somebody and tell them the most intimate details of your life, and when Lee and Truman had lunch the first time, there she is talking about her obsession with Jackie.”

Back in 1975 and 1976, chapters of Capote’s work-in-progress,Answered Prayers, were published inEsquire. His writing revealed Radziwill and Kennedy Onassis' most salacious secrets, which resulted in Capote’s excommunication from their social circle.

“She hardly knows this guy and what is he doing? He goes out the door, he tells everybody,” Leamer says, later adding, “He talks about how Jackie looked more like a man, which is a pretty insulting thing to say about the president’s widow and how incredible looking Lee was.”

Lee Radziwill (left) and Jacqueline Kennedy.Dave Allocca/Starpix/Shutterstock ;Getty

Lee Radziwill and Jacqueline Kenned

Dave Allocca/Starpix/Shutterstock ;Getty

Although the siblings' feud over what Leamer says was money, men (Radziwill dated Aristotle Onassis before he married Kennedy Onassis in 1968) and status was made public, but the sisters were there for each other behind closed doors when times got tough.

When JFK wasassassinatedin 1963, Radziwill,who died in 2019, flew to Washington D.C. from her London home to comfort her sister. When asked about their rivalry in 1976, Radziwilltold PEOPLE, “It’s just the most ludicrous talk in the world. We’re exceptionally close and always have been.”

Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.

Still, that rivalry always seemed to linger. When Kennedy Onassis died in 1994, her will revealed she would not beleaving any moneyto her younger sister.

“I’ve made no provision in this, my will, for my sister, Lee B. Radziwill, for whom I have great affection because I have already done so during my lifetime,” it read.

source: people.com