Inside Kylie Jenner's Star-Studded 21st Birthday Bash (Exclusive)

The 'Keeping Up With the Kardashians' star went all-out for her 21st birthday, and ET has the exclusive details.

Kylie Jenner is 21! 

The Keeping Up With the Kardashians star celebrated her birthday surrounded by friends and family at h. wood Group's Delilah in West Hollywood on Thursday night, and ET has the exclusive details. 

Kylie's sisters, Khloe, Kim and Kourtney Kardashian, as well as Kendall Jenner, were all in attendance and posted up a storm of pics with the birthday girl. According to ET's source, Kim's husband, Kanye West, was never far away, as he and Kim were side-by-side all night long. Khloe's boyfriend, Tristan Thompson, was missing from the festivities, as was Kylie's brother, Rob Kardashian. But Kylie's boyfriend, Travis Scott, was seen cuddling up to the woman of the hour in sweet photos. 

Both of Kylie's parents, Kris and Caitlyn Jenner, also stepped out to celebrate their baby girl, and even appeared to put their past differences aside for the evening. ET's source says that Caitlyn, who attended the party with her rumored girlfriend, Sophia Hutchins, was a bit reserved, but she and Sophia spent time chatting with Kris and her boyfriend, Corey Gamble. Sophia then hung out with the Kardashian-Jenner sisters. 

Newly single Kourtney was spotted at a table with her ex, Scott Disick, while stars like The Weeknd, Bella Hadid, Justine Skye, Chris Brown, Jordan Clarkson, Kevin Durant, Dave Chapelle, Cara Delevingne, Draya Michele and Ashley Benson also had fun at the party. As for the ball pit captured in several celebs' Instagram Stories, ET's source says it was located in Delilah's back private room, as a fun area for everyone to jump in and take photos. 

Celeb party planner Mindy Weiss worked with Revelry Event Design to craft Kylie's big bash, ET's source says, as the entire interior of Delilah was transformed to fit Kylie's pink theme. Draping, fringe, furniture and lightbulbs all captured the effect inside, while the exterior of the venue was covered in pink mylar fringe. Flowers hanging from the ceiling were by Jeff Leatham. 

The night's food was by Delilah, and party favors included pink Jell-O shots and branded Solo cups that read "Single," "Taken" and "Complicated." Avion Tequila gummy bear shots were also served by staff working the party, who wore T-shirts adorned with a photo of Kylie's Forbes magazine cover in honor of the birthday girl. 

According to ET's source, the new mom's party began at 10 p.m., but really started to get going at 11, and of course ran well into Friday morning. "Goodnight," Kylie hilariously captioned a photo of two Barbies meant to replicate her and Jordyn Woods, which had been posed on her birthday cake, early Friday morning. 

See more on the reality star in the video below.