New details have emerged about Prince William and Prince Harry’s alleged fallout.

Royal biographer Robert Lacey, who is also the official consultant on Netflix’s "The Crown," has updated his book "Battle of Brothers: William and Harry – The Inside Story of a Family in Tumult" with added chapters and new material. In the original book, which was published in 2020, the British historian addressed the ongoing woes impacted by the royal family.

In new excerpts published by the U.K. Times on Saturday, the veteran writer further explored the alleged feud between the brothers.

Rumors of a split came to light in 2019 when British bestselling author Katie Nicholl claimed that after Harry announced his engagement to Meghan Markle in 2017, William grew increasingly worried for his brother and his whirlwind romance with the American actress.

PRINCE CHARLES ‘CAN’T DEAL’ WITH PRINCE HARRY’S COMMENTS BECAUSE HE’S ‘IMMENSELY SENSITIVE,' AUTHOR SAYS

British historian and writer Robert Lacey pictured at the Edinburgh International Book Festival where he talked about his popular books about the British monarchy.

British historian and writer Robert Lacey pictured at the Edinburgh International Book Festival where he talked about his popular books about the British monarchy. (Photo by Colin McPherson/Corbis via Getty Images)

"William was quite concerned that the relationship had moved so quickly," Nicholl claimed in the TLC documentary "Kate V. Meghan: Princesses at War?". "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," Nicholl continued. "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."

Now, Lacey wrote that although relations between the princes improved by the time Harry, 36, and Markle, 39, tied the knot in May 2018, they worsened in October 2018 when William, 39, learned that a senior palace aide made bullying allegations against Markle.

According to Lacey, William confronted Harry after he learned of the allegations. However, it led to a "fierce and bitter" argument. That confrontation led to William removing Harry and Markle from the joint office they shared.

MEGHAN MARKLE REVEALS WHAT HELPED HER DURING A YEAR OF BEING 'FORCED APART'

Prince Harry, Duke of Sussex, Meghan, Duchess of Sussex, Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge and Prince Charles, Prince of Wales attend the Commonwealth Day Service 2020 on March 9, 2020, in London, England.

Prince Harry, Duke of Sussex, Meghan, Duchess of Sussex, Prince William, Duke of Cambridge, Catherine, Duchess of Cambridge and Prince Charles, Prince of Wales attend the Commonwealth Day Service 2020 on March 9, 2020, in London, England. ( Photo by Phil Harris - WPA Pool/Getty Images)

"William threw Harry out," a friend alleged, as quoted by the outlet.

Lacey alleged that the angry confrontation first occurred over the phone and then in person when William asked Harry about the bullying claims.

"When Harry flared up in furious defense of his wife, the elder brother persisted," read the excerpt. "Harry shut off his phone angrily, so William went to speak to him personally. The prince was horrified by what he had just been told about Meghan’s alleged behavior, and he wanted to hear what Harry had to say. The showdown between the brothers was fierce and bitter."

Lacey also alleged that William’s wife, Kate Middleton, had been "wary of Meghan from the start." He also claimed that William told a friend he thought the former "Suits" star had an "agenda" and that the accusations he was hearing supported that theory.

PRINCE CHARLES HONORS PRINCE WILLIAM’S BIRTHDAY IN TOUCHING INSTAGRAM POST

Royal author Robert Lacey alleged that Prince William (right) and Prince Harry had "a fierce and bitter" argument over Meghan Markle following bullying allegations.

Royal author Robert Lacey alleged that Prince William (right) and Prince Harry had "a fierce and bitter" argument over Meghan Markle following bullying allegations. (Getty)

William allegedly told a friend he felt "hurt" and "betrayed" as he’s always felt it was his duty to protect his younger brother. However, the British crown – and everything it stands for – came first.

"Harry, for his part, was equally furious that William should give credence to the accusations against Meghan, and he was fiercely combative in his wife’s defense," the excerpt read.

A rep for the Duke and Duchess of Cambridge, as well as the Duke and Duchess of Sussex, didn’t immediately respond to Fox News’ request for comment. However, Markle’s team strongly refuted the bullying allegations when they were first reported by the Times in March shortly before the couple spoke to Oprah Winfrey in a televised interview.

"The Duchess is saddened by this latest attack on her character, particularly as someone who has been the target of bullying herself and is deeply committed to supporting those who have experienced pain and trauma," a spokesperson for the Duke and Duchess of Sussex said in a statement sent to Fox News on Wednesday.

MEGHAN MARKLE TALKS NEW BOOK 'THE BENCH' AND ITS NON-TRADITIONAL DEPICTIONS OF MASCULINITY AND DIVERSITY

Pregnant Meghan Markle and Kate Middleton

Robert Lacey's book alleged that Kate Middleton (right) was "wary" about Meghan Markle. (Getty)

"She is determined to continue her work building compassion around the world and will keep striving to set an example for doing what is right and doing what is good," the statement added.

Lacey previously told Fox News that at one point, William turned to his uncle, Earl Charles Spencer, to see if he could talk to Harry about his concerns.

"Let’s make clear that William’s reservation wasn’t whether Meghan was right for Harry, but whether she was right for the royal family and royal life," Lacey explained. "When it came to Kate, William was slow and cautious. He followed duty. Harry immediately fell in love and discovered a new destiny for himself, a new meaning in his life. William saw Meghan as a self-made woman who created her own celebrity and wealth in the process. The royal family, on the other hand, is in the business of representing values."

"Royals are expected to know their place," Lacey continued. "And Harry, of course, was expected to marry a nice girl named Henrietta or Gabriella who lived in the provinces of Britain in the countryside and settle down. But Meghan and Harry both made it clear they wanted to do so much more than that. And let’s just say there are things that you can and cannot do when it comes to running the royal family and what it stands for."

VERDICT FROM MEGHAN MARKLE’S BULLYING INVESTIGATION COULD BE DELAYED TO 2022: REPORT

Britain's Catherine, Duchess of Cambridge, Prince William, Duke of Cambridge, Meghan Markle and Prince Harry leave St Mary Magdalene's church after the Royal Family's Christmas Day service on the Sandringham estate in eastern England, Britain, December 25, 2017. REUTERS/Hannah McKay - RC117DF76700

Robert Lacey previously told Fox News that at one point, William turned to his uncle, Earl Charles Spencer, to see if he could talk to Harry about his concerns. (AP)

When Harry finally announced he and his wife were stepping back as senior royals, Lacey said their grandmother, Queen Elizabeth II, suggested setting up a family lunch meeting to discuss the negotiations regarding the exit.

He said the reigning monarch was aware of the Duke and Duchess of Sussex’s unhappiness and wanted to make things right. However, one royal refused to attend.

"There was one prince who said, ‘No, I’m not going to come to lunch and sit with my brother,’" Lacey alleged. "‘I am absolutely furious. I don’t think I can be trusted to keep my temper in his company.’ And which brother was this? It was William who refused to go to the family lunch and who would only negotiate with Harry round a table."

"Both sides lost their tempers, which resulted in some bitter negotiations," Lacey alleged. "The relationship between the two brothers certainly did deteriorate. I think their respective bad tempers and anger played a big role in this."

CLICK HERE TO SIGN UP FOR THE ENTERTAINMENT NEWSLETTER

FILE - In this Nov. 11, 2018 file photo, Meghan Markle, Duchess of Sussex, attends the Remembrance Sunday ceremony at the Cenotaph in London. Meghan Markle’s father appealed to his daughter to call him, saying on Monday, Dec. 17, 2018, that they hadn’t been in touch since her wedding to Prince Harry in May. (AP Photo/Alastair Grant, File)

Meghan Markle’s team has strongly refuted the claims published by the U.K. Times. (AP)

Lacey said it will take a while for the relationship to heal.

"I think it would always have happened that Meghan and Harry would live on the other side of the world," he explained. "I think Meghan and Harry will remain based in North America. Unless the brothers can find a way to reconcile, they will have to go their separate ways and keep mutual respect for each other."

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 towards the former "Suits" star. The family now resides in the coastal city of Montecito, Calif.

In the wake of quitting royal duties, they gave an explosive TV interview to Winfrey, in which the couple described painful comments about how dark their son 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.

CLICK HERE TO GET THE FOX NEWS APP

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

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

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, whose family nickname is Lilibet, and his late mother, Princess Diana.

The Associated Press contributed to this report.