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Prince William and Prince Harry’s relationship has allegedly remained strained.

The brothers reunited on Thursday to unveil a statue of their mother, Princess Diana, on what would have been her 60th birthday. The event in the Sunken Garden at London’s Kensington Palace was their second public meeting since Harry and his wife Meghan Markle stepped away from royal duties over a year ago.

True Royalty TV co-founder Nick Bullen told Fox News the reconciliation between the two brothers would "be very difficult."

"It is still very much a work in progress. An awful lot has been said between the two. So much dirty linen has been put out in the public, so to speak."

The award-winning documentarian has been making programs about the British royal family for nearly 20 years and has worked closely with their father, Prince Charles, for eight. The streaming platform celebrated Diana’s birthday by launching a collection of documentaries, including two U.S. premieres: "Diana: A Mother’s Love" and "Diana at 60."

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Despite the rumored royal rift, Prince Harry and Prince William reunited in the U.K. to honor what would have been Princess Diana's 60th birthday.

Despite the rumored royal rift, Prince Harry and Prince William reunited in the U.K. to honor what would have been Princess Diana's 60th birthday. (Getty)

According to Bullen, sources have told him that despite the reunion, William, 39, couldn’t ignore his fury toward his younger sibling who has recently spoken out about the royal family in a bombshell interview with Oprah Winfrey, as well as on the Apple TV+ docuseries "The Me You Can’t See."

"I am told William is absolutely furious at how Harry and Meghan have shared their views about the royal family, about their own immediate family, with the world’s press," Bullen claimed. "I think it’s going to be incredibly tough to come back from that, on all sides. Harry and Meghan feel they haven’t been supported by the monarchy. But ultimately, William is a king in waiting. Duty to him comes first. His duty is to protect the crown and to protect the institution. And that’s what William is going to do."

Markle, 39, 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 a year later.

The Duke and Duchess of Sussex's departures from royal duties began in 2020 over what they described as the media’s intrusions and racist attitudes toward the former "Suits" star. The couple eventually moved to the coastal city of Montecito, California. On June 4, they welcomed a daughter named Lilibet "Lili" Diana.

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This image provided by Harpo Productions shows Prince Harry and Meghan, Duchess of Sussex, in conversation with Oprah Winfrey.

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

In the wake of quitting royal duties, the Duke and Duchess of Sussex gave an explosive interview to Winfrey, which was watched by nearly 50 million people globally. During the sit-down, the couple said painful comments were made 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.

Harry, 36, confirmed rumors that he and his brother had been growing apart, saying "the relationship is space at the moment." He added that "time heals all things, hopefully." Harry also revealed that their father didn't accept his calls for a time.

Days after the broadcast, William responded, telling reporters: "We are very much not a racist family."

Bullen said that the brothers were in touch to prepare for the statue unveiling. However, those conversations were allegedly brief.

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The brothers were previously seen together in April for the funeral of their grandfather Prince Philip. The Duke of Edinburgh passed away on April 9 at age 99.

The brothers were previously seen together in April for the funeral of their grandfather Prince Philip. The Duke of Edinburgh passed away on April 9 at age 99. (Mark Large-WPA Pool/Getty Images)

"I’m told the boys have been communicating by text, but they’re relatively short texts," he claimed ahead of the unveiling. "But they are communicating."

While Bullen noted that the brothers were doing "everything" they could to keep things civil at the statue unveiling, there’s no doubt that their mother "would have been heartbroken" over their strained relationship.

"If Diana were around today, I think she would have banged their heads together like any mother," he said. "I’m told by people that knew her well that she would regularly sit the boys down and say to them, ‘You only have each other. You two are the only ones who know what it’s like to go through this life. You have to look after each other.' And they did. They were such an amazing team for so long."

"I remember filming them on a number of occasions and they were just dynamite together," Bullen recalled. "I think she would have been distraught at the current state of affairs."

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Britain's Meghan, Duchess of Sussex talks with Britain's Prince Charles, Prince of Wales as Britain's Prince William, Duke of Cambridge, talks with Britain's Prince Harry, Duke of Sussex, as they all attend the Commonwealth Day service at Westminster Abbey in London on March 11, 2019.

Britain's Meghan, Duchess of Sussex talks with Britain's Prince Charles, Prince of Wales as Britain's Prince William, Duke of Cambridge, talks with Britain's Prince Harry, Duke of Sussex, as they all attend the Commonwealth Day service at Westminster Abbey in London on March 11, 2019. (RICHARD POHLE/POOL/AFP via Getty Images)

And William isn’t the only one who’s been affected by the Duke and Duchess of Sussex’s revelations.

"I’m told that their father, the Prince of Wales, is really hurt by everything that he’s heard, everything that’s been said," Bullen claimed. "He was incredibly welcoming to Meghan Markle. He really embraced her and really enjoyed having her be a part of the family. When he walked her down the aisle on her wedding day, it was his way of welcoming her with open arms. He certainly wasn’t expecting this outcome."

Despite the royal rift, Bullen said that ultimately, Diana would want her sons to be happy. Still, he believes she would have wanted them to patch up their differences and maintain a strong bond as they embark on different paths.

"As William steps closer to the throne, it will become an increasingly lonely and isolated position," said Bullen. "The boys once knew they only had each other. And so, to not have your brother by your side must be very sad. I think Diana would have been very sad about that."

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Princess Diana, seen here with Prince William and Prince Harry, died in 1997 at age 36 from injuries she sustained in a Paris car crash.

Princess Diana, seen here with Prince William and Prince Harry, died in 1997 at age 36 from injuries she sustained in a Paris car crash. (Anwar Hussein/Getty Images)

Bullen is hopeful that one day, William and Harry will ultimately reconcile, both publicly and privately. 

"They know what they’ve got to do, and I’m sure they will do everything they can to get it right," he said.

The Associated Press contributed to this report.