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How serious are Selena Gomez and The Weeknd? Only as serious as Selena is about her latest music project, according to Justin Bieber insiders.

Sources close to the Biebs tell TMZ he thinks The Weeknd, who was spotted making out with Selena last week, is being used for what he can do for Selena, music-wise.

Insiders say Justin believes his ex did the same thing with previous guys she was working with, including Nick Jonas and Zedd. TMZ adds that Selena and The Weeknd have been collaborating in the studio.

If Justin's miffed about seeing Selena kiss a new guy in the tabs, he didn't show it over the weekend, when he and his rumored former hookup pal Kouertney Kardashian met up at the Peppermint Club in Los Angeles on Saturday, Jan. 14.

Sources tell Us Weekly that Justin, who arrived with friends including Liam Payne, showed up before Kourtney, who didn't stick around for more than 15 minutes.

Their hang seems like more than a coincidence though -- they got together later at Delilah, where they hung out until around 2 a.m., according to Us.

Though the two have been said get flirtatious when they're around each other, a source said this time the hang was platonic.

"They were just there as friends, with friends," said a source, "and and it was not romantic."

Kourtney is rumored to be seeing model Younes Bendjima; the dark-haired duo met in October during Fashion Week. Last month, they were seen leaving a hotel together.