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What do you mean you're not hooking up with Justin Bieber, Kourtney Kardashian?

The eldest Kardashian is adamantly denying reports that she and the "Sorry" singer are fooling around, but multiple usually-credible media outlets are saying otherwise. Justin, too, is apparently saying otherwise.

"Justin bragged to friends recently that he has been hooking up with Kourtney Kardashian," a source told Us Weekly,

Another source said, "Oh, yeah, that's definitely happening and has been for some time now…Every time Kourtney and Justin are together they're extremely flirtatious. They text each other all the time."

According to TMZ, the duo's fling started in October when they ran into each other at Los Angeles hotspot, The Nice Guy. After that, Kourtney flirted and Justin went in for the kill, so to speak.

Us reports that the duo had dinner at Nice Guy in October, as well. "When he was there with Kourtney, he was such a gentleman and so nice and respectful," the source said. "He was definitely trying to impress Kourtney and act more mature." They later when to the Universal Studios for the "Halloween Horror Nights" attraction.

They've hooked up multiple times, TMZ said, including this past weekend, where they hit up the Nice Guy again and headed to a karaoke lounge. Kourtney was seen leaving Justin's hotel at 4 am.

Kourtney has allegedly told her family that this is much ado about nothing and she's only hung out with Justin in a group setting.

"He's single, she's single and they're just having a good time," a source told TMZ, "nothing serious."

Gossip Cop also reported that the odd couple is "casually hooking up," but it's nothing serious.

Certainly aware of the reports, on Dec. 14 Justin left many wondering if he was taking a dig at Kourtney's ex, Scott Disick on Instagram, but posting a photo of a girl in a compromising position. The girl's face can't be seen in the image, but many wondered if it was Kourtney, considering Justin captioned the image "lord knows," perhaps in reference to Scott who calls himself "Lord Disick."

Alas, though, it was revealed that the woman in question was not Kourtney.