Kourtney Kardashian and ex Scott Disick reunite for Mason Disick's Bar Mitzvah party

Kourtney Kardashian and ex Scott Disick's eldest son Mason Disick celebrated his 13th birthday with his family and friends at a bar mitzvah party Dec. 17.

The guest of honor's parents, who broke up in 2015 and co-parent their three kids, were photographed arriving separately at the venue, the Offsunset lounge in West Hollywood. Scott walked in with their youngest child, son Reign Disick, 8,

Kourtney's sister Khloe Kardashian shared photos from inside the party, posting shots of herself with Mason's sister Penelope Disick, 10, and Kim Kardashian's eldest daughter North West, 9.

"Mazel Tov Mason!!!" the Good American founder wrote on Instagram. "The girls and I attempted to take some pics."

Others spotted at the bash: Kim, son Saint West, 7, Kylie Jenner and Kendall Jenner and family matriarch Kris Jenner.

Mason, whose dad Scott is Jewish, is the eldest of the momager's 12 grandchildren. The now-teen is the first junior member of the famous family to have a bar mitzvah, a Jewish coming-of-age event.