WENN 1 / 7

A family feud seems to be brewing between the Kardashian family and Caitlyn Jenner.

According to a new report in Us Weekly, Caitlyn's upcoming memoir, "The Secrets of My Life," is the catalyst for the fight.

Us said on April 19 that Kris Jenner read an advance copy of her former spouse's book and the family is "upset" about what Caitlyn wrote. The transgender activist didn't tell the family in advance what was being written about them.

"Cait's talking about the family but didn't speak to them first, just like she did with the Vanity Fair interview," the insider said referring to magazine's spread in which she debuted her new look. "They're tired of being caught off guard."

In the book, Caitlyn, who was married to Kris for 22 years and recently underwent gender reassignment surgery, said the family matriarch "made her suppress her true self," sources said.

The book also reportedly contains explicit details from Kris and Caitlyn's sex life when she was living as Bruce Jenner. People magazine obtained excerpts in which Cailtyn said she was "imbued" with love.

"My attitude is no different than it was in high school: I'm just not entirely comfortable with it," she allegedly wrote. "Since -- let's not kid ourselves -- everyone wants to know, Kris and I have good and frequent sex at the beginning."

She also discusses how much Kris knew about her gender identity struggles.

"This will always be a subject of dispute between us. She insists that she was taken by surprise by my ultimate transition to Caitlyn, which obviously means in her mind that she did not know enough," Caitlyn writes.

The Kardashian girls are backing their mom in light of all this.

Kourtney, Kim and Khloe Kardashian do "want Caitlyn to be happy and share her experience, but also to be sensitive to Kris," the source said.

A pal of Khloe's added, "This is the last straw. Khloe doesn't identify with this person who seems to have stopped caring for the family."

"The Secrets of My Life" will be released on April 25.