Kourtney Kardashian and Justin Bieber Aren't Hooking Up, Source Says: 'She Wouldn't Go There'

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Kourtney Kardashian and Justin Bieber are not having a May-December romance, a source close to Kourtney tells ET.

Despite recent reports that the 36-year-old reality star and the 21-year-old pop star have been hooking up, the source says the two are just "good friends."

"Kourtney wouldn't go there," the source adds.

WATCH: Kourtney Kardashian Gets a Ride Home from Pal Justin Bieber

Rumors surrounding Kourtney and Justin reached a fever pitch over the weekend, when Kourtney attended Bieber's surprise show at celeb hot spot The Nice Guy in West Hollywood, California on Friday. A source told ET that the two "were nearly inseparable" throughout the night.

On Sunday, Justin seemingly added more fuel to the fire when some thought he was taunting Kourtney's ex, Scott Disick, on Instagram. The singer shared a picture of himself provocatively standing over an unidentified woman reclining on a black Audi, and curiously captioned the pic, "Lord knows"-- which some thought was a direct jab at Scott's "Lord Disick" nickname. TMZ later confirmed that the woman in the photo is not Kourtney.

Kourtney and Justin have both yet to directly address the rumors. However, we do know that the two are longtime family friends and neighbors, and have known one another for years. In October, Justin Instagrammed a photo of the pair hanging out at Universal Studios Hollywood for its "Halloween Horror Nights." The two spent about an hour and a half together at the park, going through several haunted mazes, before heading to the Saddle Ranch Chop House restaurant at Universal CityWalk. Justin was walking with his arm around Kourtney and joking with her about being scared, an onlooker told ET at the time.

Justin is also notably close to Kourtney's younger sisters, 18-year-old Kylie Jenner and 20-year-old Kendall Jenner. In March, he also showed that he's friendly with Kourtney and Scott's children. The "Sorry" singer Instagrammed a photo of himself giving 6-year-old Mason a piggyback ride in the pool. Kourtney's mother, Kris Jenner, re-Instagrammed the shot, writing, "#Mason & @JustinBieber family pool day!!! #bestbabysitterintheworld."

WATCH: Justin Bieber Shows Concern for Kylie Jenner: 'It's F**ked, Bro, This Lifestyle'

Check out the video below to see how Kourtney celebrated both her sons Mason and Reign's Dec. 14 birthdays a little earlier on Saturday at her home. A source told ET Scott was in attendance, despite rumors swirling around her and Justin.