Looks like Kim isn’t the only Kardashian to be dealing with relationship drama…

It is being reported that Scott Disick, baby daddy and long-time boyfriend of Kourtney Kardashian, had an affair with reality star Kristin Cavallari!

A close friend of the Kardashian clan confirms that “Scott and Kristin hooked up in Las Vegas during a time (February 2009) that he was on a break from Kourtney.”

According to the source, Kourtney and Scott were good friends with Kristin while she was filming Laguna Beach and even after Kristin stopped dating Kourtney’s stepbrother Brody Jenner.

Apparently, the three were close until Kourtney caught Scott with Kristin on a date at Apple Lounge in LA on March 11, 2009.

But this wasn’t just a one night stand, ” Scott and Kristin were hooking up on and off for a year, maybe even two,” a second Kardashian friend reveals. “When Kourt and Scott would fight, he’d party with Kristin and hook up.”

She and Kristin have changed from friends to enemies. “She and her sisters have called Kristin ‘the whore bag’ ever since.”

So with all this past drama, it only seems natural that there was tension when Kourtney’s brother, Rob Kardashian, was revealed to be on Dancing with the Stars with who else but the ‘whore bag’ herself, Kristin Cavallari.

“Scott and Kourtney argued about Kristin,” a friend confirms. “Kourtney can’t stand her now and didn’t want Scott at show tapings.”

This is why you’ll notice that Scott was absent from all tapings until late October long after Kristin had been eliminated.

So now things are not going so well with the couple and an insider has revealed that Scott had moved out of their New York suite and into his own room at the Gansevoort Park Avenue while taping Kourtney and Kim Take New York.

“I’m seeing Scott slip back into his old patterns,” Kourtney admits in the soon to come premiere of Kourtney & Kim Take New York.

Two Kardashian couples down, one to go.

Better stay on your toes Lamar!