Prince Harry, Meghan Markle's exit from UK still leaves Prince William 'simmering with resentment': author

Prince William is celebrating his 41st birthday on Wednesday – and some royal experts believe the occasion is bittersweet for the future king.

The Prince of Wales’ fractured relationship with his younger brother, Prince Harry, is said to have deepened following the Duke of Sussex’s explosive memoir "Spare," which was published in January. In it, the 38-year-old wrote of his struggles with royal life, often in eyebrow-raising detail.

The brothers were once inseparable, bonded by the loss of their mother, Princess Diana, and their royal journeys. It had always been believed that the brothers would continue to support each other as they continued their paths within the British monarchy.

Harry’s story is dominated by his rivalry with his elder brother as well as the death of their mother. Harry described how growing up, he was tormented by his status as royal "spare" behind William. He recounted a longstanding sibling rivalry that worsened after Harry began a relationship with Meghan Markle, an American actress, whom he married in 2018. The couple made their exit from the U.K. in 2020 and moved to California.

"William is still simmering with resentment over ‘Megxit,’ not to mention Harry's unflattering portrait of him in ‘Spare,’" Christopher Andersen, author of "The King," told Fox News Digital. "In the book, Harry portrays his older brother as his "archnemesis" – Harry's words – a scolding, overbearing, brooding and, at times, even violent man."

"Harry is still obviously upset that William was given a free ride because he is the heir – that William got away scot-free with doing many of the same things Harry was excoriated for," Andersen said. "William is doing a marvelous job of compartmentalization. He seems to have put Harry and Meghan in a box and shoved that box into a remote corner of his mind – all so that he can do the job he must do as Prince of Wales."

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In "Spare," Harry said that during an argument in 2019, William called the Duchess of Sussex "difficult," "rude" and "abrasive" before grabbing him by the collar, ripping his necklace and knocking him down. During their alleged argument, Harry said he suffered cuts and bruises from landing on a dog bowl. William later apologized.

Harry said their father, King Charles III, implored the brothers to make up, saying after the funeral of Prince Philip in 2021, "Please, boys. Don’t make my final years a misery."

It wasn’t the first time Harry, 38, spoke of his deteriorating relationship with William.

In the Netflix docuseries "Harry & Meghan," which became available for streaming in December 2022, Harry said William shouted at him during a meeting about his plans to step back as a senior royal.

"It was terrifying to have my brother scream and shout at me and my father say things that simply weren’t true, and my grandmother quietly sit there and sort of take it all in," said Harry.

The breakdown of the brothers’ relationship allegedly started before the Duke and Duchess of Sussex said "I do." In 2019, Vanity Fair correspondent and royal author Katie Nicholl participated in the TLC documentary "Kate v. Meghan: Princesses at War?" which aimed to examine whether there is any truth to the speculation of unrest following Markle, 41, becoming part of the British royal family.

In the special, Nicholl said William was increasingly worried about his brother and his whirlwind romance with the former "Suits" star following their engagement in late 2018.

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"William was quite concerned that the relationship had moved so quickly," Nicholl said at the time. "And being close to Harry, you know, probably the only person close enough to say to Harry, ‘This seems to be moving quickly. Are you sure?’ And I think what was meant as well-intended brotherly advice just riled Harry."

"Harry is hugely protective of Meghan," continued Nicholl. "He saw that as criticism, he interpreted that as his brother not really being behind this marriage, this union. And I don’t think things have been quite right ever since."

During the Duke and Duchess of Sussex’s televised interview with Oprah Winfrey in 2021, Harry described his relationship with William as "space at the moment."

"And time heals all things, hopefully," he added.

British royals expert Hilary Fordwich told Fox News Digital that William was "horrified" by the tell-all, which was viewed by nearly 50 million people globally.

"[It] signified the first betrayal of their inner sanctum of trust," she said. "… [But] like his grandmother, Prince William has his eye on the long game. … He is, by all his actions, distancing himself from his wayward brother."

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"Disassociation is protection for the crown and therefore an imperative," she added.

Andersen said that William has been leaning on his wife, Princess Kate Middleton, for support.

"With help from the formidable Kate, who never lets on that she is perturbed by anything, William is awfully good at concealing his disappointment," Andersen said. "In photographs with his wife and children, interacting with King Charles and Queen Camilla or performing his official duties, William looks happier and more content than ever."

"Beneath the surface, it's a different story," he continued. "Of course, he had always expected Harry to be at his side on the Buckingham Palace balcony. Of course, Harry is the only other person on the planet who knows what it was like to be doted on and smothered with motherly love by Princess Diana. Harry is also the only person who knows what it was like to cope with Diana's sudden death. The tie between them went beyond any normal brotherly bond. It has to be deeply scarring to see that bond severed."

Kinsey Schofield, the host of the "To Di For Daily" podcast, told Fox News Digital that William's relationship with Kate, 41, has been essential during the ongoing rift.

"Prince William was very picky in choosing his life partner, and I think that decision has been incredibly beneficial to him over the last several years," said Schofield. "The love and support he has received from his wife and children have been crucial to his heart and healing. We will continue to see a gentle and dedicated father and a smitten husband. William is kind and charming like Princess Diana."

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"Inevitably, Harry is going to need his brother, and I think Prince William will be there to catch him when he falls," Schofield said. "But there will be no reconciliation while Harry continues to burn bridges and hurt the people that William loves the most."

The Duke and Duchess of Sussex cited the British media’s treatment as one of the main reasons for their decision to quit royal duties and move to the U.S.

"Spare" gives no sign that royal family relations will be repaired anytime soon. Harry told ITV in an interview to promote the book that he wants reconciliation but that there must be "accountability" first.

In the final pages of the memoir, Harry described how he and William walked side by side during the funeral procession of Queen Elizabeth II in September but spoke barely a word to one another.

"The next day, Meg and I returned to the United States," he wrote.

When Harry visited his home country in May for his father's coronation, he left London just hours later. The transatlantic trip is more than 5,400 miles, or about an 11-hour nonstop flight. During Harry's brief appearance, William seemingly avoided eye contact.

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According to reports, the Duke and Duchess of Sussex weren't invited to Trooping the Colour, the annual public celebration of the monarch’s birthday. And just months prior in March, a spokesperson for the couple confirmed that they were asked to vacate Frogmore Cottage, their home in the U.K. This suggested a further fraying of ties within the royal family.

"There seems to be no real interest on the part of either brother to repair all the damage that's been done," Andersen said. "Besides, they both have plenty on their plate. William has assumed a huge burden as Prince of Wales. The future of a teetering monarchy rests squarely on his shoulders. Meanwhile, Harry and Meghan are scrambling to ink huge deals that will make them tons of money and essentially keep them in the game of being ‘relevant.’"

"The one person in the entire world who not only knew William’s beloved mother but who shared his tumultuous childhood won’t be by his side," Fordwich said. "Worse yet, it’s highly unlikely there will be either communication or reconciliation."

The Duke and Duchess of Sussex live in the wealthy coastal city of Montecito in California with their two young children.

The Associated Press contributed to this report.