Rob, 29, is currently battling with issues including social anxiety, and it has been alleged that he's not getting on with his family – particularly 34-year-old Kim.
Now momager Kris, 59, is thought to be considering taking legal action against Rob to stop him writing an expose on the family.
An insider revealed to Radar Online: "Everyone knows that if Rob wrote a book, it would be an absolute gold mine.
"But Kris is willing to do whatever is needed to stop him and prepared to fire off a cease and desist letter if she finds out that he is going to start the process of doing this book.
"Kris does not want to do this to her son, but this book would be such a slap in the face and undoubtedly a best-seller."
It comes after Rob took to social media to compare Kim to Rsoamund Pike's character Amy Dunne in Gone Girl.
Sharing a picture of blood-soaked Amy, Rob wrote: "This is my sister Kim, the b*tch from Gone Girl…"
Khloe, 30, recently opened up about her brother, admitting that he is not in a good place right now.