The 36-year-old reality star invited her 32-year-old ex-partner to celebrate what would have been the attorney's 72nd birthday with her family. Robert Kardashian died of cancer at age 59 in 2003.
Kourtney and her family ate Armenian food in honor of her late dad's heritage, as seen in a live stream on sister Kim Kardashian's website and app. Kim's daughter, North West, dressed as Elsa from Frozen, while Kourtney's daughter, Penelope Disick, dressed as Anna.
"You know it's been a good night when you've finished your family dinner and you realize Elsa's sister Anna left her hair behind. #penelope #frozen #magical night," Kris Jenner, Kourtney and Kim's mom and Robert Kardashian's ex-wife, captioned a photo of the dinner table.
Jenner, who is also mom to Khloe Kardashian and Rob Kardashian with her late ex-husband, hosted boyfriend Corey Gamble and Khloe's estranged husband, Lamar Odom, in addition to her family. Kourtney's sons Mason Disick and Reign Disick were also present.
Kourtney and Disick were together for nine years before splitting in July. The pair previously came together for the Thanksgiving holiday, but their reunion Monday was overshadowed by reports Disick spent the previous week partying at New York Fashion Week.
"He was a total mess," a source told People of Disick, who has struggled with substance abuse issues for years. "He was doing well for a long time. It's sad and worrisome ... Hopefully he can go back to being healthy. He doesn't want to disappoint Kourtney or his kids."