Star magazine recently reported that Kendall Jenner had sex with future brother-in-law Scott Disick at a party while half-sister Kourtney Kardashian was pregnant with third child Reign.

"After their partying episodes, he saw Kendall as an adult," an insider said. "A superhot and fun one at that."

Jenner and Disick have been spotted out in public together lately, and the insider claimed that Kardashian has been increasingly uncomfortable with the way her husband is "checking out" her younger sibling.

How did the mother of Mason and Penelope react when the pair's mutual friend told her the shocking news?

"At first, Kourtney was in complete shock and disbelief, but after she processed the information, she was devastated," the insider claimed. "She started screaming at [Scott], calling him 'sick.' But he kept denying it. He stormed out, and the next she heard of him, he was doing what he always does -- drinking his problems away. This time it wasn't in Las Vegas, it was in Aspen."

Not only did Kardashian allegedly confront Disick, but she also questioned Jenner, Star reports.

"Kendall denied everything, then accused her mom of being happy about the rumors because they will raise her precious TV ratings," the source said. "This is what their relationship has turned into. What should be a brotherly/sisterly love has become sexualized. Scott clearly finds her attractive, and she likes the attention. It's just wrong."

According to the insider, Kardashian is not speaking to either one of them and claims "they're dead to me."

HollywoodLife.com, however, reports Kardashian is sick of the media attention surrounding the Kardashian/Jenner clan.

"Kourtney doesn't believe the rumor. She just doesn't. She can't," a source said. "All this has done is reignite the disappointment she has for Scott, and she's desperately in need of time away from him and her entire family before she loses it. This is the one time in her life that she hates being a Kardashian. She's on the verge of a mental breakdown, and she's about to explode. She has so much on her plate right now and feels no one really cares. She just gave birth, but Scott's been MIA most of the time. And when he's around, he's acting reckless."

Khloé Kardashian took to her Twitter accounts on Wednesday to poke fun of the recent report.

"I'm really pissed about this whole @KendallJenner and @ScottDisick thing!! Scott, I thought it was you and I that was having the affair!" she wrote.

Jenner also took part in the joke, tweeting:

How does matriarch Kris Jenner feel about all this alleged family drama?

"Normally, Kris is all for drama because it keeps them in the headlines, but this time she's at a loss," the insider told Star magazine. "She's too worried about her grandchildren to cash in on this scandal. She even confronted Kendall about it.

Another source HollywoodLife.com said Kris finds the rumor "repulsive and beyond disgusting."

"Scott has his issues and his demons, but she believes he has integrity when it comes to knowing right and wrong within the family dynamic. And Scott's not the issue: she raised Kendall better than that and all the sisters are bonded tighter than cement," the source said.  "Is Scott banging Kendall? Get the hell out of here. No. He's a mess ... don't get me wrong, but he's not banging his would be sister-in-law."