The Kardashian and Jenner girls got seriously sassy in a new group photo showing them all flipping off the camera.
The whole gang of sisters, as well as mom Kris Jenner, got together to hang out and party in honor of Kylie's birthday.
"BIRTHDAY BEHAVIOR! WERE ALL TURNING 21," Kylie wrote in a caption of the photo on Instagram.
In addition to the bold photo, Kris also sent a heartfelt birthday message out to Kylie.
"Happy 21 st birthday to my baby!!!!! You are my youngest, my beautiful angel, and it has been life’s greatest reward to watch you grow into an amazing young woman who is the most incredible mom to [Stormi], business woman, friend and daughter," the message posted to Kris' Instagram read.
"You are truly a special soul and you have the biggest heart and you are so kind and generous and thoughtful to everyone," the message continued. "I am so proud of you Kylie, and I thank God he chose me to be your mommy. I love you more than you will every know."
Many of Kris' followers commented on the post with birthday wishes of their own, with many of them sending warm sentiments.
"To think 21 years ago she was born and placed straight into your arms. She will live to do the same and share this very moment with you too," one follower said. "Happy 21st Birthday to you Kylie."
"The best of all, the coolest, the simplest, the most amazing and the most intelligent of the Kardashian /Jenner clans," another followers said of Kylie.
Over on Twitter, Kylie's big sister Kim Kardashian posted a sweet birthday message, saying that "it’s such a trip that my baby sister is 21."
Happy 21st birthday @kyliejenner baby!!!!! It’s such a trip that my baby sister is 21 😱 So happy to be on this sister and now mom journey with you forever!!!! I love you so much! You will still always be my baby sis and I’m always here for you no matter what! pic.twitter.com/gseJWjAMmR— Kim Kardashian West (@KimKardashian) August 10, 2018
"So happy to be on this sister and now mom journey with you forever!!!! I love you so much," she added. "You will still always be my baby sis and I’m always here for you no matter what!"
Interestingly, Kylie shares her birthday with a few other celebrities, including Antonio Banderas, as well as fellow reality TV stars "Mama June" Shannon and Maci Bookout.