Kris Jenner is sending out all his grandma love.

The Kardashians The 69-year-old star dedicated a sweet Instagram post full of throwback photos to grandchildren Mason, 15, and Reign, 10, whose birthday is December 14th.

“Happy birthday to my two incredible grandchildren, Mason and Reign!” She began her post about the boys, the sons of Jenner’s eldest daughter, Kourtney Kardashian, 45, and her ex Scott Disick, 41.

“Our birthday twins! “I still can’t believe you both have the exact same birthday,” she continued. “What a special blessing that binds you forever. You are both so loved and I am forever grateful to God for choosing me to be your grandma.”

Jenner then took a moment to reflect on each boy.

“Mason, you are so kind, creative, smart, talented and the best brother, son, grandson, cousin and friend,” the mother of six wrote. “Watching you grow up and become such a caring and wonderful young man is pure magic – you make us all so proud.”

“Reign, you bring so much energy, laughter and joy wherever you go,” she continued. “Your curious mind and vibrant personality brighten any room. You are smart, funny and full of so much love and I feel blessed to witness the amazing little person you are becoming. You fill my life with so much pride and happiness.”

“I love you both with all my heart and soul. I’m so proud of the incredible boys you are and look forward to the great future you both have ahead of you!” She concluded her post.

The proud grandma accompanied the sweet birthday message with a carousel full of photos showing her and her grandchildren at various ages.

Jenner – who has 13 grandchildren – recently shared that she fully accepts being “outnumbered.”

“I just need to take a deep breath,” she told PEOPLE as she discussed accommodating her six children and their children during the upcoming holidays. “There are 13 of them!” You can’t control chaos like that.

“It’s so much fun,” she explained. “I’m just such a holiday girl. I mean, I’m just obsessed with celebrating every holiday.”

Never miss a story again — sign up for PEOPLE’s free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from celebrity news to compelling human interest stories.

The reality star matriarch also noted that her family always spends Christmas morning at her house and that she is “strict” about gifts. The self-proclaimed order freak also revealed that – despite the chaos – she tries to maintain order.

“I walk around with paper towels and my all-purpose cleaner all the time,” she said. “I’ve always done that. The rest of the family is used to me.”