We never would have guessed that these two would be an item!

Jaden Smith, 14, and Kylie Jenner, 15, are dating, according to Us Magazine. "It's new, but they've been friends forever," a source tells the mag.

On Sunday Jaden and Kylie were spotted on a lunch date at Caffe Nero in London's Piccadilly Square, but prior to that Jaden was kicking it with Justin Bieber, who celebrated his 19th birthday on Friday at Cirque du Soir.

Bieber's entourage apparently got into a squabble with club security because Jaden is underage (the drinking age in the U.K. is 18), and while Bieber denied that was an issue, a source tells the mag that it definitely "caused problems." After the argument, Bieber was photographed stomping around in the street without his shirt on, and a few hours later he tweeted, "worst birthday."

Biebs later added, "Sometimes u just wanna vent and not be quiet. I love my fans though. Just gonna chill with friends. London shows this week. It ain't always easy but is what it is. Gonna stay focused." Hopefully he's not mad at Jaden!