Meghan Markle
Meghan Markle's sister, Samantha, teased about her upcoming book. Pictured: Markle attends day twelve of the Wimbledon Lawn Tennis Championships at All England Lawn Tennis and Croquet Club on July 14, 2018 in London. Getty Images/Clive Mason

Meghan Markle's sister, Samantha, has explosive revelations about the duchess and their family in her upcoming book.

Samantha recently promoted her book, "In The Shadows of the Duchess." She revealed that her work includes an "in-depth look" at the royal wedding.

"Everyone will just have to read it to see what really goes on in the shadows," Samantha said (via Express). "My book is much more comprehensive as it definitely takes an in-depth look. (It is an) in-depth look at the unspoken dynamics through and beyond the wedding."

Samantha also promised her readers that "opening the book and reading it puts a spotlight on the shadows."

Markle's half-sister previously made headlines when she revealed she was planning to publish a tell-all book titled, "The Diary of Princess Pushy's Sister." The title gained negative feedback from Markle's fans. Samantha explained that it wasn't meant as a slight against the new royal, but she eventually changed the title.

"Well, it is true that I'm writing a book and the title is accurate, what is not true [is] this unbelievable swell that's been created that it's some sort of slamming 'tell-all,'" she said. "First of all, it's only a tell-all in that I go through and recant some of the beautiful nuances of our lives, our family home."

In previous interviews, Samantha denied that there is a rift between her and Markle. According to her, she was just misquoted by tabloids. However, she also continues to rant about Markle and Prince Harry and criticize the couple on Twitter to this day.

In fact, in one of her posts, she criticized Prince Harry for tolerating Markle's behavior against their family. She also asked him to "man up." In another post, she called the Duke of Sussex a "coward."

"Harry is a 'wuss' to allow the Duchess of Nonsense to mistreat everyone who has been close to her, especially her family. Diana would be ashamed. Stop wearing Meg's skivvies and bra and take your pants off of her!" Samantha wrote on Twitter.

In her recent posts, Samantha said that Markle is the only person who can fix her issues with their father, Thomas Markle Sr. She insisted that it is "morally unconscionable" for the Duchess of Sussex to ignore their dad.

"The PR henchmen can step aside because Meg is the only one who can fix this by doing the right thing by our father," she wrote on Twitter.

"She can do the right thing by our father or regret it for the rest of her life. It is morally unconscionable to ignore him As he has made her everything that she is," she added in another post.