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Nick Bullen believes there are many lessons Prince Harry can learn from his great-great-uncle Edward VIII.

Queen Elizabeth II’s uncle had been King Edward VIII for less than a year before he famously abdicated the throne in 1936 to marry American divorcee Wallis Simpson. The couple was cut off from the monarchy following the abdication. As a result, they struggled financially and had no source of income, People magazine reported.

In 1951, Edward produced a ghost-written biography titled "A King’s Story: The Memoirs of the Duke of Windsor," which detailed his upbringing, falling in love with the socialite, and giving up his royal position. According to the outlet, royalties from Edward’s book helped fund the couple as they lived in France. Simpson released her own memoir, "The Heart Has Its Reasons," in 1956.

In 1970, the couple also gave a televised interview in which they discussed their lives and opinions.

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Edward VIII Wallis Simpson

The Duke (1894-1972) and Duchess (1896-1986) of Windsor (formerly Edward VIII and Wallis Simpson) at their home, the Villa La Croe in Cap D'Antibes, Cannes in France. (Photo by Fox Photos/Getty Images)

"It’s fascinating when you draw the parallels between the two," Bullen told Fox News. "Both of them married divorced American women. We all know that, but it goes much deeper than that. Edward and his brother also experienced their own sibling rivalry can be compared to Harry’s strained relationship with his brother, Prince William."

"But Edward and his brother Bertie [King George VI] never really resolved their differences," the co-founder and editor-in-chief of True Royalty TV continued. "And when Edward wrote his book, it was really the first time a senior member of the royal family had written such a book. And he was paid a fortune at the time. It may have even been the highest-paid book of its time. It had a tremendous impact. So what kind of impact will Harry now have?"

Bullen is an award-winning documentarian who has been making programs about the royal family for nearly 10 years and has worked closely with Prince Charles for eight.

This month, True Royalty TV is releasing several new documentaries, including "The Royals Revealed: Harry and Edward, Princes in Exile," which explores the similarities between the royals, including their military aspirations, wives, sibling rivalry and eventual exit from royal duties.

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The Duke of Windsor (1894-1972), formerly King Edward VIII, with his memoirs, entitled "A King's Story: The Memoirs of the Duke of Windsor," circa 1951. (Photo by Erika Stone/Getty Images)

"The big lesson viewers will learn from this documentary is how the Duke and Duchess of Windsor sort of faded into obscurity and became bit players on the world stage," said Bullen. "They were slightly awkward guests at dinner parties in New York. It raises the question, how long will Harry and [his wife] Meghan Markle’s value stay at such a high level? I think this documentary is a window to a story that has happened before and what could occur again."

In July, Random House announced that the Duke of Sussex, 36, was writing an "intimate and heartfelt memoir." The book, currently untitled, is expected to be released in late 2022.

"I’m writing this not as the prince I was born but as the man I have become," said Harry in a statement. "I’ve worn many hats over the years, both literally and figuratively, and my hope is that in telling my story — the highs and lows, the mistakes, the lessons learned — I can help show that no matter where we come from, we have more in common than we think. I’m deeply grateful for the opportunity to share what I’ve learned over the course of my life so far and excited for people to read a firsthand account of my life that’s accurate and wholly truthful."

Financial terms were not disclosed. However, Harry will donate proceeds to charity, according to Random House.

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Prince Harry will be releasing a memoir in 2022. (Kevin Mazur/Getty Images for Global Citizen VAX LIVE)

"Prince Harry will share, for the very first time, the definitive account of the experiences, adventures, losses, and life lessons that have helped shape him," Random House announced.

Bullen said that no matter what Harry chooses to share in his book, it will certainly rock the monarchy just as Edward’s tell-all did at the time.

"Even though Harry wasn’t the king and he didn’t abdicate, he still has a major impact on the monarchy," Bullen explained. "I think the biggest lesson – or warning – that this documentary shares is the fact that Edward and Wallis Simpsons faded slowly into obscurity. They eventually became irrelevant. Will the same happen to Harry and Meghan as Prince William’s children take to the world stage? It may seem far from now, but it will happen. What will happen to Harry and Meghan 10 years from now? Will they be the same stars they are now? Some historians have suggested that this is unlikely."

According to Bullen, history has shown that those who leave behind the royal family struggle to carve out their own identities.

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Article on the front page of the Daily Express about American socialite Wallis Simpson (18961986). Simpson's relationship with King Edward VIII (18941972) eventually led to his abdication. (Photo by Ann Ronan Pictures/Print Collector/Getty Images)

"Edward, like Harry, was the absolute golden boy of the royal family," Bullen shared. "He was adored by people across the world wherever he went. If you look at our films, you’ll see archived footage of crowds cheering for him. And even after his marriage to Wallis, there was still this golden glow around him. However, that quickly faded."

Still, Bullen said there’s one myth that continues to exist when it comes to Harry’s relative.

"The truth is, I think Edward was happy enough to step away from the throne," he said. "He is sometimes portrayed as a man who lived with regrets, that he wished he could have continued as king. But I think he was actually pretty comfortable with his decision. And that’s something we tend to forget about him."

"He wasn’t a man who was sitting in Paris longing to be back on the throne," he shared. "I think he had regrets about how he was able to serve his country and how he wasn’t able to make the difference he thought he might have been able to as a younger man. But I don’t think he regretted giving up the throne because he was very much in love with Wallis. And he left to be with the woman he loved."

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Edward Wallis Simpson TV interview

The Duchess and the Duke of Windsor interviewed in the lounge of their Parisian residence, a mansion of the wood of Boulogne.  (Photo by Robert Siegler / INA via Getty Images)

Edward died in 1972 at age 77 from cancer. Simpson’s close friends surrounded the duchess and in later years, her name surfaced mainly in lawsuits over alleged media intrusions. In one, she won damages from a French magazine whose photographers scaled the wall of her villa.

Simpson died in 1986 at age 89.

Markle, a former American actress, became the Duchess of Sussex when she married Harry in May 2018 at Windsor Castle. The couple welcomed a son named Archie Harrison Mountbatten-Windsor in 2019.

The Duke and Duchess of Sussex’s departures from royal duties began in 2020 over what they described as the British media’s intrusions and racist attitudes toward the former "Suits" star, 40. The family now resides in the coastal city of Montecito, California.

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Prince Harry Meghan Markle Oprah Winfrey interview

This image provided by Harpo Productions shows Prince Harry, from left, and Meghan, The Duchess of Sussex, in conversation with Oprah Winfrey. (AP)

In the wake of quitting royal duties, they gave an explosive TV interview to Oprah Winfrey in March, in which the couple described painful comments about how dark Archie’s skin might be before his birth. The duchess talked about the intense isolation she felt inside the royal family that led her to contemplate suicide.

Buckingham Palace said the allegations of racism made by the couple were "concerning" and would be addressed privately.

On June 4, the couple welcomed their second child, a daughter named Lilibet "Lili" Diana Mountbatten-Windsor. The child is eighth in line to the British throne.

The name pays tribute to both Harry’s grandmother the queen, whose family nickname is Lilibet, and his late mother, Princess Diana.

The Associated Press contributed to this report.