Kourtney Kardashian Says Sons' Shared Birthday Is 'One of the Best Days of My Life'

Kourtney Kardashian Instagram

Kourtney Kardashian is cherishing her sons' special day.

Both Reign, 8, and Mason, 13, celebrate their birthdays on Dec. 14 — the two brothers born five years apart.

"December 14th… one of the best days of my life, twice and forever. my birthday boys," the mom-of-three — who also shares daughter Penelope, 10, with ex Scott Disick — wrote on Instagram.

Alongside her message, the Poosh founder, 43, posted a cuddly throwback photo of the bonded brothers in their PJs.

RELATED: Kourtney Kardashian's Cutest Family Pictures with Her Kids

Her sister Kim Kardashian, in a Instagram tribute of her, shared a current photo of Kourtney's oldest on her Stories.

"The day has come when you're taller than me now," the proud aunt wrote over a photo of a grown-up looking Mason wearing a back-pack and black sunglasses. "I just love who you are and I'm just so proud of you Mason."

"Welcome to your teenage years. Happy Birthday," she added.

RELATED: Kris Jenner Celebrates Grandsons Reign, 8, and Mason, 13, on the Brothers' Shared Birthday

Kim Kardashian Instagram

Earlier in the day, grandma-of-twelve Kris Jenner shared a special post for her grandsons, calling them "two of the brightest lights in my life."

"Mason, you are my first-born grandson, and I am so very proud of you each and every day!" Jenner, 67, began. You've grown into such an amazing young man, and I adore you."

"Reign, you are the funniest!!!!" she added of the second birthday boy. "You are one special guy with so many facets to your personality!!!"

"Both of you have the most amazing qualities and are kind, considerate, loving, so smart, so talented in so many ways, and such a special magical part of our family … AND it's wild that you were born on the very same day!!!! Five years apart!!!!"

RELATED: Here's Everything You Need to Know About Kourtney Kardashian and Travis Barker's Blended Family

Kourtney has been vocal about wanting another child, though shared in September that she and husband Travis Barker have taken a break with their IVF journey,

She regularly expresses her gratitude for her blended family, including a scene on the season finale of The Kardashians in which the group gathered together for dinner.

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"Our family's expanding and growing and we have so much to be thankful for," Kourtney explained in a confessional, in reference to Barker's teenagers with ex Shanna Moakler: Landon, 19, and Alabama, 16. He is also a step-father to Moakler's daughter, Atiana De La Hoya, 23.

"I love the idea of a blended family," she continued. "I think that the more kids, the merrier. You have all these siblings and more people to love. It's a beautiful thing."