Kourtney Kardashian Celebrates 'Birthday Twins' Mason and Reign in Sweet Instagram Tribute

Kourtney Kardashian is celebrating a very special day.

The Keeping Up with the Kardashians star, 42, posted a series of Instagram photos in honor of her sons, Mason, 12, and Reign, 7, who were both born on Dec. 14.

"Happy birthday to my birthday twins five years apart," the mom of three captioned the adorable collection of photos of them throughout the years. "I couldn't have dreamed up anything like them for my sons, I feel so blessed and grateful for these two boys and all that they bring to my life."

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

The love didn't stop there, though. On Mason and Reign's actual birthday on Tuesday, Kardashian posted a slew of videos on her Instagram Story, including an "Elf-182" concert setup with Blink-182's "All the Small Things" playing in the background, while a handful of Elf on the Shelf figurines rocked out on stage. Kardashian also tagged her fiancé, drummer Travis Barker, in one of the videos.

RELATED VIDEO: Kourtney Kardashian and Travis Barker Make Sweet TikTok with Her Daughter Penelope, 9

This is the latest of many recent birthday celebrations in the Kardashian-Jenner family. In November, Kardashian celebrated Barker's 46th trip around the sun, captioning a collection of photos of the pair, "I f------ love you more than anything. My favorite everything. Happy birthday to you my baby!"

The couple vacationed in Mexico with their kids to commemorate the momentous occasion, going horseback riding at sunset, spending time together as a family, and more.

Kardashian and Barker, who have been dating since January, got engaged in October at the Rosewood Miramar resort in Montecito, California.

"Since this is Kourtney's first engagement, it's of course a big deal," a source previously told PEOPLE, detailing Barker's romantic proposal. "Most of her family was there to celebrate. Two of Travis' kids were there too. They enjoyed a private, family dinner at the hotel."

Added the source: "It was a beautiful celebration. Everyone is very happy for them. Her family loves Travis."