Admitted cheater KRIS JENNER is carrying on a shocking secret relation­ship with one of the men rumored to be the biolog­ical father of her daughter KHLOE!

Sources say the suspicious liai­son blew up after a neighbor caught a half-naked Kris planting a kiss on her hunky hairdress­er of 30 years, Alex Roldan.

Now the 57-year-old Kardashian “momager” is des­perate to keep the true nature of her red-hot relationship with Alex, 56, under wraps for fear it will end her troubled marriage to Bruce Jenner, the sources add.

“Kris and Alex have been friends for decades, but re­cently they’ve been spending more and more time together,” revealed a family in­sider.

“She’s been con­fiding in him about her struggles with Bruce, and they’ve also bonded over re­ports claiming Alex is Khloe’s real dad.

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

That blew up in their faces when the source says the two were bust­ed during an intimate moment.

“Kris was in the back area of Alex’s salon for a hair treatment,” said the insider. “She removed her shirt to put on a protective cape – but then accidentally dropped it and was left standing there in a sheer, plunging bra.

“Alex quickly ran over with a towel to cover up Kris’ exposed breasts. She made a comment about how chivalrous he was, then gave him a kiss.

“It just so happens that one of Kris and Bruce’s neighbors was at the salon and caught a glimpse of the clinch. She didn’t say anything at the time, but word quickly got back to Bruce.”

Bruce later confronted his wife of 22 years and all hell broke loose, according to the source.

“Rather than apologize, Kris told Bruce she wished he were more mature like Alex,” said the insider.

“Kris likes the fact that Alex is tall and brawny with a full head of hair and piercing eyes, which Kris says is the oppo­site of Bruce’s man boobs, scrawny legs and whiny personal­ity.”

Now, Kris’ inner cir­cle is buzzing about her new “fling,” said the source.

“Her friends are calling Alex her ‘boyfriend,’ and her daughters are giv­ing her grief,” said the insider. “They’re furious that Kris is disrespecting Bruce by carrying on with Alex.”

Over the years, Kris and Alex have had no qualms about ap­pearing together in public, sources say, even sharing a lun­cheon date with Kris’ daughter Kourtney and her partner Scott Disick in New York City in 2011.

A published report recently named Alex as Khloe’s biologi­cal father and claimed that Kris made Alex – who opened his L.A. salon in 1985 – sign a $30 million nondisclosure agreement to keep him from spilling the beans about the true nature of their relationship.

BUT as The ENQUIRER has reported, 28-year-old Khloe believes she’s the result of an affair between her mother and O.J. Simpson and has even invit­ed the disgraced football great to live with her after he’s freed from prison.  Meanwhile, Kris has been branded as a serial cheater.

As The ENQUIRER reported, Bruce caught his wife rekindling her passionate relationship with boytoy Todd Waterman – who was her lover during her marriage to the late Robert Kardashian.

Adding to 63-year-old Bruce’s ire, Kris cavorted through France with her hunky trainer, Gunnar Peterson, 50, during a vacation last summer.

As we’ve reported, Kris’ kinky past also includes a three-way romp with O.J. Simpson and his then-wife Nicole Brown Simpson in the late ’80s as well as a pur­ported secret sex tape.

In a bid to save their crumbling union, Kris and Bruce began seeing marriage counselors in July 2012. But Bruce later se­cretly contacted lawyers about divorcing Kris in what could lead to a nasty battle over their $180 million fortune.

“Kris’ interest in Alex is put­ting her bank account and her relationship with her children at risk,” said the insider.

“But it’s really no surprise. Kris is just doing what she always has – putting herself and her own needs first.”