The Kardashian family took to social media to wish Kourtney a happy birthday.
Kourtney, mother to Mason, eight, Penelope, five and three-year-old Reign, turned 39 on Wednesday.
Her younger sister, Kim, posted her best wishes on Instagram.
Alongside a picture of the pair on holiday in the Turks and Caicos Islands, she said: “Happy Birthday to my friend I’ve had the longest in my life! Wouldn’t know what to do without you! Have the best birthday ever!!!!”
And Kim was not the only member of the famous family to send a very public happy birthday message.
Kourtney’s mother, Kris, posted an adorable throwback picture of the pair together, with a young Kris cradling a baby Kourtney.
She captioned the picture: “Happy birthday @kourtneykardash!!!! My first born, my gift from God, my amazing precious blessing!!
“You have given me so much joy and love and beautiful immeasurable experiences and memories since the day you were born and I thank God every single day that he chose me to be your mom.
“I’m so proud of you… you are the most amazing mom, sister, auntie and daughter and I love you with all of my heart forever and ever Mommy xo.”
Meanwhile, Kourtney’s brother, Rob, took to Twitter to wish his big sister a happy birthday.
Alongside a picture of Kourtney with their late father, Robert, he wrote: “Happy Birthday to my oldest and wisest Sister ! I LOVE YOU so much!!! I am so Thankful for you and God Bless You with another amazing year! Love Bob.”
The Kardashians welcomed the latest member of the family last week when Kourtney’s sister, Khloe, gave birth to a daughter, True Thompson.