While the Kardashian-Jenner crew joined together to celebrate Kendall's big day with two separate parties -- a dinner at Catch LA before heading over to West Hollywood hot spot Delilah -- on Wednesday, they also took to social media (what else?) to send the supermodel their birthday wishes.
Kendall's momager, Kris Jenner, was the first to wish the model a happy birthday, with a sentimental collage of pictures from Kendall's childhood.
"Happy 21st birthday my sweet angel, @kendalljenner!!!!! You are so beautiful inside and out," she captioned the sweet snap. "Thank you for being YOU and for blessing us with your kindness, your adorable sense of humor and your love. I am blessed beyond belief to call you my daughter. You make me proud every single day, and I love you so much!!! Happy birthday my beauty!!! #lovemommy #proudmama."
Khloe Kardashian took to her app to share an adorable pic of Kendall from 2000, along with a sweet note for the birthday girl.
"My little Kendall is all grown up!," she wrote. "I could not be more proud of the amazing (not to mention fierce AF!!!!) young woman that you have become. Your first legal drink is on me, boo! ? Happy birthday!"
"My big sister is 21 ? happy birthday Kenny," Kylie captioned an Instagram post alongside a vintage snap of the two in costumes. "My other half. I wouldn't be me if it weren't for YOU ❤️? we dreamt about the day when you'd turn 21 & I'd be 19. It came too fast ? ... But who you are and where you are today was beyond my wildest expectations! You are an angel my supermodel sister. I love watching you live out your dreams. Every Kylie needs her Kendall @kendalljenner."
Caitlyn Jenner also took to Instagram to share her well wishes with a photo of the two from Kendall's 21st birthday dinner.
"School, track practice, cheerleading practice, all that carpool! Now my little girl is 21!" she wrote. "Wow, so proud of you, happy birthday."
Kendall's siblings Rob and Kim Kardashian have yet to post on social media, however Kim did make an appearance at the model's birthday bash.
"She was really happy to be able to celebrate her sister's 21st birthday," a source tells ET of Kim, who snuck through the back door of the party with husband Kanye West. "Kim looked really happy to be out with her family. She was smiling and talking to everyone."