Meghan Markle is at the center of a looming controversy yet again as her estranged half-sister, Samantha Markle, will finally release her tell-all book.

The Diary of Pushy's Sister, Part 1, will be up for sale in the U.S. on Jan. 17, and it promises to dish out the "hidden truths" about the Markle family, especially Samantha's life with Meghan. According to Daily Mirror, the tell-all's release in the U.K. is still uncertain because the country's laws against libel are different from the U.S.

The book has, so far, been deemed as a potential "best seller" on the Barnes & Noble site. In 2017, Samantha announced that she was writing the tell-all and warned her sister that she won't like some of the content. Samantha also said that the royals would be appalled by what Meghan did to her own family, which she will detail in the book.

Sources said that Meghan was upset to know that her sister was writing a memoir based on her when they barely bonded as siblings. The two have been estranged long before the Duchess of Sussex married Prince Harry, the Duke of Sussex, in 2018. There's at least a 17-year-gap between Meghan and Samantha, who have the same father, the former lighting director Thomas Markle.

Prior to the royal wedding, Samantha heavily criticized her sister in U.K. TV talk shows and on Twitter. Meghan was still talking to her father at that time and asked him to make Samantha stop talking to the press.

When Samantha was not invited to the royal wedding, she became more critical of her sister. She also confirmed in an interview with Jeremy Vine that she traveled to London from Florida to have a one-on-one with Meghan, but Palace guards apparently barred her from seeing the Duchess of Sussex.

In 2019, Samantha said that she has started penning her second book, In the Shadows of the Duchess. It will be another exposition of her life as Meghan's older sister.

Meanwhile, Meghan's relationship with her father also crumbled in 2018. The two are set to face off in a legal battle this year, which could be "traumatic" for the royal family. A source said that this trial will not just be about Meghan but it will also expose the operations of the Palace and its staff members, who will likely be asked to take the witness stand.

Thomas is a witness for the defense, the Associated Newspapers, which the Duchess of Sussex is suing for breach of privacy. The publication extracted Meghan's private letter to her father to run as a story that painted her in a bad light, the lawsuit claimed.

By mid-January, lawyers of the Duchess of Sussex will argue for a summary judgment, instead of an actual trial. If the judge accepts the argument, then the case will be dismissed.