Kim Kardashian and Kylie Jenner celebrate Kris Jenner's 68th birthday

Kim Kardashian and Kylie Jenner have celebrated Kris Jenner's 68th birthday.

The Kardashians stars took to Instagram on Sunday evening to pay tribute to Kris on her 68th birthday.

"Happy Birthday to the best mom in the entire world! It's so hard to put into words what you mean to me and all of your children," Kim, 43, captioned a series of black and white photos of her and Kris. "Your level of support is unmatched. You are the definition of unconditional love. And we all feel it so deeply."

"I know I'm so lucky to have you as my mom and best friend," the Skims founder continued. "I cherish you and never take anything you do for us for granted. You are the Queen that started it all and continue to make all of our dreams come true. I LOVE YOU MOM @krisjenner."

Meanwhile, Kylie took to her Instagram Stories to share a sweet photo of her and Kris sporting matching black leather dresses as they each held a martini, Kris's go-to drink.

The 26-year-old beauty mogul captioned the photo, "happy birthday mommy. !!!! @krisjenner."

Kylie also shared a sneak peek of Kris's birthday celebration at WAGYUMAFIA, posting a photo of the menu.

Additionally, Kris's longtime boyfriend Corey Gamble posted his own tribute to mark the special day.

"Happpppy Birthday my beautiful queen Love you through life twice ....." the 42-year-old wrote on Instagram. "Keep being the powerful force of love & wisdom that guides the ship that you birthed and built... I'm always proud of you & thankful for u.... love you forever birthday girl. Keep shining and being the BEST mother to your 6."

Kris and Corey reportedly began dating in 2014 shortly after they met at a party in Ibiza.