More details are coming to light about Prince Harry and Meghan Markle's departure as senior members of the royal family -- and a majority point to a particular bitterness between the Duchess of Sussex and her sister-in-law, Kate Middleton, Duchess of Cambridge.

Parts of the upcoming royal biography titled "Finding Freedom," written by Omid Scobie and Carolyn Durand, were released the U.K.'s The Times this week. The book involves claims of contention between the royal brothers and their wives from palace insiders.

The book, set to be released next month, paints a dark picture of the palace behind-the-scenes amid Harry and Meghan's monumental "Megxit," with insiders claiming that the "establishment" was in fear that the Duchess of Sussex's massive popularity "might eclipse that of the royal family itself."

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Prince Harry and Meghan, the Duke and Duchess of Sussex arrive at the annual Endeavour Fund Awards in London on March 5, 2020. (AP)

Shortly after Prince Harry and Meghan's January announcement and subsequent travels to Canada, the couple returned to the United Kingdom where Meghan was essentially snubbed by Kate, according to the biography.

"Although Meghan tried to make eye contact with Kate, the duchess barely acknowledged her," the authors write.

Scobie reacted to the revelation in an interview with The Times.

"To purposefully snub your sister-in-law...I don't think it left a great taste in the couple's mouths," he said.

The book also includes revelations from inside sources who backed up claims of the royal family's distaste for Meghan, a Los Angeles, Calif. native. She and Harry "liked being in control of their narrative," according to the authors, but they allegedly found themselves in William and Kate's shadow.

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The book claims that Harry and Meghan would be told to hold off on their projects until Prince Williams or Prince Philip made announcements of their own endeavors.

From left, Britain's Prince Harry, Prince William, Meghan Duchess of Sussex and Kate, Duchess of Cambridge leave the annual Commonwealth Service at Westminster Abbey in London Monday March 9. (Phil Harris / Pool via AP)

"There were just a handful of people working at the Palace they could trust," one friend of the Sussexes claimed.

In turn, Harry believed staffers at the palace "simply didn't like Meghan," one source told the authors.

Meanwhile, Harry and Meghan's departure as senior members of the royal family left William and Kate "hurt," the book claims.

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One source said "some" of the royal family members blame Meghan. In the midst of Harry and Meghan's decision to split their time between the United Kindom and North America, a friend claimed Meghan said she gave up her "entire life for this family."

Meghan Markle, Duchess of Sussex and Prince Harry, Duke of Sussex visit District 6 Museum on Sep. 23, 2019 in Cape Town, South Africa. (Getty)

"I was willing to do whatever it takes. But here we are. It's very sad," the friend claimed Meghan said.

Reps for Harry and Meghan confirmed to Fox News on Saturday that the couple played no part in the upcoming biography.

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“The Duke and Duchess of Sussex were not interviewed and did not contribute to ‘Finding Freedom’. This book is based on the authors’ own experiences as members of the royal press corps and their own independent reporting," the reps said in a statement.

Meghan and Harry are currently residing in Los Angeles. While the two reportedly made security upgrades to the home they're living in for extra privacy, the royal couple recently filed a lawsuit against photographers for deploying drones to capture images of them and their son Archie.