The Kardashian family seems to have left a bad taste in one of the ladies' most recent exes' mouths as he is now reportedly threatening to expose all of their secrets in a tell-all book if they don't back off.

According to Radar Online, Kourtney Kardashian's now ex-boyfriend, Younes Bendjima, sent a "clear message" to her, stressing that if she doesn't get her sisters to stop hounding him, he'll put all of their skeletons in writing.

His alleged threat comes after two of Kourtney's famous sisters, Kim and Khloé, took to Instagram to publicly attack him as he tried to refute claims that he cheated on the oldest of the bunch.

"Younes had one of his friends reach out to Kourtney to tell her that if her sisters don't stop talking s**t about him that he would write a tell all book and air all of their dirty laundry," an insider told the site.

The source added that, since he and the mother of three were together for two years, the male fashion model "knows more about the family than anyone else that has come in and out of their circle in quite some time."

"She does not want this to escalate anymore so she asked her family to refrain from saying anything about him," the insider added. "At this point, she just wants him to go away so she can move on with her life."

Younes and Kourtney recently split shortly before he was seen frolicking on the beach with socialite and Tyga's former flame, Jordan Ozuna, in Mexico.