AceShowbiz -

Caitlyn Jenner has gone too far in her forthcoming memoir "The Secrets of My Life", which is billed as a book in which she "reflects on her past as she looks to her future." As Caitlyn touches on a number of sensitive topics like three failed marriages and sex reassignment surgery, her stepdaughter Kim Kardashian reportedly fears about being trashed in the book.

"Kim is majorly freaked out right now about what Caitlyn might say in her tell-all book about herself and Kanye [West]," a source tells HollywoodLife.com, before adding, "Caitlyn knows a lot of Kim's secrets." Citing the insider, the webloid alleges Kim will never talk to Caitlyn again if she does "any damage to Kim, her brand, or her relationship with her husband."

Though the memoir has yet to be released, the Kardashian sisters are reportedly banding together against the 67-year-old former Olympian over the fact that she uses the new book to trash their late father Robert Kardashian, Sr. According to an excerpt obtained by Radar Online, Robert confessed to her that he knew O.J. Simpson murdered his ex-wife Nicole Brown Simpson in the late 1990s.

"They feel like Caitlyn had no right to talk about their dead father Robert," a close friend to the Kardashian-Jenner clan tells the publication, before adding, "Any relationship that Caitlyn had with Kim, Khloe and Kourtney is going to be completely gone now!" The source continues, "The Kardashian girls have a very high tolerance for bulls**t, but where they draw the line is when anyone talks bad about their dad."