Meghan Markle's half-sister Samantha Markle has claimed she would reveal "hidden truths" about the British royal in a tell-all memoir.

In the memoir, which Samantha has titled "The Diary of Princess Pushy's Sister Part 1," she has written about her dysfunctional relationship with the former American actress. The bombshell book, which Samantha had announced in 2016, will be released in the United States next Friday.

American bookseller Barnes & Noble promises the book will expose "hidden truths about her (Meghan's) family, as a royal fairy tale plummets from the tea towels." The description of the 330-page novel reads: "Things are not always as they seem, in a world where social labels define who we are, how we live, and how we view each other. Samantha Markle finds herself caught in between the cross hairs of media mayhem, when she reveals hidden truths about her family."

It also notes that "things are not always as they seem" and sometimes the "truth is stranger than fiction."

It is believed that Meghan and Samantha last met in 2008. However, Samantha has been highly critical of Meghan in her interviews and was supporting her father Thomas in his much-publicised feud with the "Suits" alum. Samantha labelled her sister a "shallow social climber" and blamed her for freezing out their father and other members of the family, calling her "inhumane" and "the Duchess of Nonsense."

According to a report in Mail Online, Meghan had burst into tears after discovering that her estranged half-sister was planning to write an explosive memoir about her. The Duchess of Sussex reportedly felt that she was being "taken advantage of" by Samantha.

Samantha had announced the novel in April 2016, eight years after she last met Meghan and just weeks after the actress' romance with Prince Harry became public. She announced last year that she would be writing a second book, which will be titled "In the Shadows of the Duchess."

Samantha lives in Florida, while Meghan moved to her first-independently bought home in Santa Barbara with husband Prince Harry and son Archie last year. According to "Finding Freedom," a biography about Harry and Meghan and their exit as senior royals written by Omid Scobie and Carolyn Durant, Meghan and Samantha have not seen each other in more than a decade. The book also says that the half-sisters had bumped into each other only twice since they were children.

Thomas Markle shares Samantha, 56, with ex-wife Roslyn Markle, and Meghan, 39, with ex-wife Doria Ragland.

Meghan Markle
Meghan Markle Michele Spatari/AFP