Kardashian reportedly broke up with boyfriend of two years Younes Bendjima shortly after they returned from a long European vacation. Since then, Kardashian has been enjoying the single life, though family members like Khloé Kardashian continue to joke about them finding their way back to each other.
"Sofia is furious that Scott and Kourtney are hanging out again," a source told InTouch, "She understands that they have to remain civil for the kids but has become convinced that Kourtney is trying to steal back her man."
Kardashian and Disick share three kids from their nine-year relationship, Mason, 8, Penelope, 6, and Reign, 3.
"She recently reached out to her and told her to back off," the source added.
The outlet writes the Keeping Up With the Kardashians star has been leaning on her baby daddy since the spit from Bendjima.
"Scott's caught in the middle," the source said. "He loves Sofia but will always have a soft spot for Kourtney."
When news of Kardashian's breakup with Bendjima first surfaced, reports said Disick was "very happy" about the split.
"Scott is very happy Kourtney cut it off with Younes. Although he is happy in his relationship with Sofia, he never liked Younes for Kourtney," a source told E! News at the time.
"Scott and Kourtney are in a cordial place right now. Scott is always resistant to rock the boat with Kourtney," the source added. "He truly will always care about her as wants her to be happy. Everything is always better for the kids' sake, when they are in a good place."
The couple split in July 2015, though the Kardashians are all still very close to Disick.
"In the beginning, Scott was making fun of Kourtney for dating someone so young and saying it would never last," another source told E! News. "Once he got with Sofia, he couldn't say anything about Younes. It gave him a lot of perspective and understanding that age is just a number. It was hard for him to see Kourtney dating and he was looking for any reason to not like Younes. But since being with Sofia, he has moved on. Scott cares a lot less than he used to. Of course, Kourtney has a very special place in his heart and always will. He wants Kourtney to be happy."