The claim was made by Princess Diana’s biographer, Andrew Morton, who recently penned a book about the late royal titled "Elizabeth & Margaret: The Intimate World of the Windsor Sisters," which explores their fierce devotion for each other, and the tensions they endured along the way.
For his book, Morton was able to track down some of Margaret’s closest confidants, former palace aides, as well as numerous insiders who knew the women over the years. Margaret passed away in 2002 at age 71.
"It was incredibly difficult for Margaret," Morton told Fox News about Queen Elizabeth II’s younger sister and her divorce. "She was a deeply Christian woman who had her own desires that often conflicted with her faith. And she struggled. She desperately wanted the marriage to work, but there were too many challenges."
In 1960, Margaret married society photographer Antony Armstrong-Jones. It was the first royal wedding to be televised and was welcomed by the country as a joyous occasion for a princess who finally found love. It had been five years since she made her widely publicized decision to end her romance with divorced war hero Peter Townsend after pressure from church leaders, political figures and her own family.
The couple welcomed a son in 1961, followed by a daughter in 1964.
But the union was an unhappy one. Armstrong-Jones, who became Earl of Snowdon, had conducted multiple affairs, History.com reported. According to the outlet, when Margaret and Roddy Llewellyn, a landscape gardener and aristocrat 17 years her junior, were photographed frolicking on a private island, Armstrong-Jones used the scandalous shots as an excuse to leave the already strained marriage.
The relationship had long been plagued with scandal before then. It is believed Armstrong-Jones’ first major affair was in 1969 with Lady Jacqueline Rufus-Isaacs, daughter of the Marquess of Reading, the Evening Standard reported.
"He was [also] having an affair with the wife of his best man and he was bisexual," Morton claimed. "So after the marriage, he was having casual affairs. The queen and the queen mother were not as sympathetic as one would think. They adored Armstrong-Jones and called him charming. So the royal family wanted to keep the marriage together, especially for the sake of the children. But eventually, it became too much to bear. Margaret was lonely. And the whole thing of both parties seeing other people just became an open secret."
"It was a mess," he added.
Armstrong-Jones’ relationship with Camilla Fry, the wife of his best friend Jeremy Fry, resulted in a love child named Polly Fry, Newsweek reported. According to the outlet, Polly grew up believing Jeremy was her biological father. However, a 2004 DNA test confirmed she was actually Armstrong-Jones’ daughter. Polly was born three weeks into the royal couple's honeymoon.
In "The Crown," the series alleged that Armstrong-Jones had a three-way relationship with the Frys, a rumor that was substantiated by Anne de Courcy’s 2008 biography titled "Snowdon," Town & Country reported.
"Finding out at the age of 45 that the man I had idolized and put on a pedestal higher than Nelson’s Column since I was a small child was not in fact my father was a hard burden to bear," Polly told U.K.’s DailyMail in 2008. "Rather than being twisted with guilt and shame at what I’ve done in uncovering a secret that I should have been told long ago, I can just carry on being little old me, the person I am today."
In 1978, the couple finally divorced. It was the first royal divorce since King Henry VIII. Margaret never remarried.
"Princess Margaret’s personal life was one of sadness," said Morton. "The reality is, Margaret was a much more serious person. I was just talking to somebody who described how religious she was. He recalled seeing her praying on her own and leaving Westminster Abbey on her own. I think that image of her with a cigarette burning brightly with a bottle of Famous Grouse while partying until the early hours makes great television, but there was another side to her that was much more reflective and serious."
Armstrong-Jones passed away in 2017 at age 86. While he didn’t leave any money to Polly, she attended his funeral at Westminster Abbey, Town & Country reported. The outlet noted that before his death, he had a son in 1998 following an affair with magazine editor Melanie Cable-Alexander.
And after the suicide of 55-year-old journalist Ann Hills in 1997, it was revealed that she had known Snowdon for 20 years, had been a longtime lover and had remained a close friend.
Despite Armstrong-Jones’ rocky relationship with Margaret, he was admired for his discretion, never speaking with the media about their breakup. He also rejected offers to write a book about it.
As for Margaret, duty came first over finding love again.
According to the palace’s official site, Margaret played an active role in the royal family’s public work and supported the queen. She was the patron or president of over 80 organizations, ranging from children’s charities to ballet companies.
But as a heavy smoker for many years, Margaret suffered repeated respiratory illnesses and even had a part of her lung removed in 1985. She also had a mild stroke in 1998. Shortly before her death, Margaret’s sight had been impacted by a stroke and she was confined to a wheelchair.
Buckingham Palace said Margaret died "peacefully" in 2002.
"I hope my book will give readers a sense of who Princess Margaret really was," said Morton. "She endured many challenges and heartbreaks, but ultimately, it’s a story of devotion of not only to her sister but to the crown."
The Associated Press contributed to this report.