Earlier this month, it was reported that Justin Bieber and Kourtney Kardashian have been spending a lot of time together and that the two are dating. While neither of them have commented on the rumors, a new report claims that the two are indeed seeing each other. Moreover, the "Sorry" singer is allegedly bragging about it to his friends.

"Justin bragged to his friends recently that he has been hooking up with Kourtney Kardashian," a source told Us Weekly. The insider added that the mother of three was at Bieber's American Music Awards afterparty at the Nice Guy in Los Angeles on Sunday, Nov. 22—the party which was reportedly attended by the singer's ex, Selena Gomez.

A second source told Us that every time the reality star and the 21-year-old are together, they are "extremely flirtatious."

"That's definitely happening and has been for some time now," said the source.

Earlier this month, the pop singer and the 36-year-old reality star spent a night out in LA at the Nice Guy and at karaoke lounge Blind Dragon.

Bieber is a long-time friend of the reality star's family and earlier this year, the singer even posted a picture of him swimming at the family's pool with Mason, 6, who is the Kardashian's eldest son with ex Scott Disick. Kardashian has two more children with Disick: Penelope, 3 and Reign, 1.

Meanwhile, Disick is said to have issued an ultimatum to the singer, warning him to stay away from his children. According to a Hollywoodlife source, the 32-year-old is embarrassed that Kardashian is seeing Bieber.

"He's told Kourtney and some mutual friends of Justin's that he needs to keep his distance from his kids," said the insider, adding that Disick will "come after" Bieber if he refuses to do so.