Kourtney Kardashian, 36, gave Disick many second chances over the course of their nine-year courtship because they have three children together -- Mason, 5, Penelope, 3, and Reign Aston, 11 months.
However, the couple officially split in early July 2015 when Disick was photographed getting touchy-feely with ex-girlfriend Chloe Bartoli while vacationing in Monte Carlo.
A seemingly heartbroken Disick checked into luxury drug and alcohol rehabilitation center Cliffside Malibu in October to address his personal issues and substance abuse, but according to multiple sources, he's doing a great job of co-parenting now.
"Justin bragged to friends recently that he has been hooking up with Kourtney Kardashian," an insider previously told the magazine.
A second source added, "Every time Kourtney and Justin are together they're extremely flirtatious. They text each other all the time."
If Kourtney's fling with the "Sorry" singer actually happened, it's clearly over now, as Bieber has posted numerous Instagram photos kissing Hailey Baldwin in recent days.
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