KRIS JENNER is carrying on a secret relationship with a longtime “friend” – and it could be the last straw for her marriage to BRUCE, say sources.

In a shocking expose, The ENQUIRER rips the lid off the latest scandal involving the 57-year-old Kardashian “mom-ager,” who has a long history of cheating.

 “They’ve been friends for decades but recently have been spending more and more time together,” a family insider said about Kris and the man, who’s described as being “tall and brawny with a full head of hair and piercing eyes.”

The two were rumored to be lovers way back when Kris was married to the late attorney Robert Kardashian, and reports have surfaced that he is actually the father of one of her children!

“At first, they just laughed off the rumors,” said the insider. “But after joking about their supposed secret sex life, all the hot-and-heavy talk got their sexual chemistry brewing!”

It all exploded when they were caught in an intimate clinch – which The ENQUIRER reveals in stunning detail – and Bruce found out. He confronted Kris, and you won’t believe her reaction.

BUT you can read all about it, and discover the identity of the Mystery Man, in the latest issue of The ENQUIRER. It’s definitely one story you won’t want to miss!