On Friday night, Balmain Creative Director Olivier Rousteing hosted a belated birthday bash in the Hollywood Hills of Los Angeles, California. The super social designer was joined by friends like Jennifer Lopez, Cara Delevingne, Kate Hudson, Justin Timberlake, Jaime King and almost the entire Kardashian-Jenner-West set–Kendall Jenner, Kim Kardashian West, Kylie Jenner, Kris Jenner, and Kourtney Kardashian. Unfortunately, the Backstreet Boys–who performed at the epic H&M x Balmain show in New York earlier this week–were not in attendance. (A holdover of the Nsync rivalry, perhaps?) See all the best party photos here.