Selena Gomez and Justin Bieber appeared to be on the verge of a reunion just weeks ago, but now, rumors are swirling that Bieber is back with Kourtney Kardashian.

A short time after Gomez attended Bieber's Los Angeles concert after engaging in a flirty exchange on Instagram, the Keeping Up With The Kardashians star is said to be gushing over her sexual chemistry with Gomez's 22-year-old ex-boyfriend.

“There’s definitely an age gap there, but they have a lot of chemistry,” a source told Star magazine, according to a report by Hollywood Life on Wednesday. “[She] thinks Justin is the best lover ever. Being around Justin makes Kourtney feel young. It’s refreshing when she spends all day chasing after a bunch of rambunctious kids.”

Kardashian turned 37 earlier this week and she and her former partner, Scott Disick, have three children together, Mason, 6, Penelope, 3, and Reign, 1. However when it comes to Kardashian's children, she and Bieber are making it a point “not to flaunt their fling” in front of the children, according to Star.

Still, the source explained, “She’s joked that Justin is great with her kids, certainly more playful and fun with them than Scott ever was.”

Just one week ago, it was reported that Bieber and Gomez were back in touch after their relationship hit a rocky point around the time of the iHeartRadio Music Awards, where Bieber allegedly ignored Gomez completely.

“Justin and Selena are talking over text but it is a little strained between the two right now,” a source tells Hollywood Life last Wednesday. “But as much as it isn’t getting romantic right now, things change every second with these two that by the weekend if Justin is lonely, he will probably start putting on the charm to get her interested again... Just another day between these two, they can’t stand each other and they can’t stand being without each other.”

For more on Bieber's up and down relationship with Gomez, check out the video below.