Rob Kardashian just resurfaced on Instagram for a celebratory occasion.

The Arthur George founder, who is protective of his privacy and mainly remains off-camera, recently made a rare comment on social media, sharing a sweet tribute in honor of his sister Khloe Kardashian's 39th birthday.

"Happy Birthday @khloekardashian," Rob wrote on Instagram June 27 alongside a picture of the duo. "Wishing you nothing but good health and happiness forever my darling buttercup!"

He also expressed his appreciation for the Good American mogul and posted a snapshot of her with his 6-year-old daughter Dream Kardashian, who he shares with ex Blac Chyna.

"I love you so much and so thankful to have u in my life and for all that U do for Dream and I," Rob added in his tribute to Khloe. "I don't know what I would do without you happy birthday."

And she seemed moved by his message. 

"My baby!!!!" Khloe replied in the comments. "My favorite human being in the world. You're my heart beat."

While Rob has largely stepped back from the spotlight in recent years—with his Instagram bio stating his mom Kris Jenner's company runs his account—he has occasionally posted birthday messages. He previously paid tribute to his late father Robert Kardashian in February.

However, Rob wasn't the only one to wish Khloe a happy birthday as the family matriarch shared an enthusiastic note of her own.

"Happy birthday to my beautiful bunny @khloekardashian!!!!" Kris wrote on Instagram next to a video set to Stevie Wonder's "You Are the Sunshine of My Life" that showed footage of Khloe from over the years. "Khloé you are the sunshine of my life… You are the most amazing daughter, mommy, sister, auntie, best friend, neighbor, and such a huge part of my heart!!!!!"

Kris went on to call Khloe—who shares daughter True Thompson, 5, and son Tatum Thompson, 11 months, with ex Tristan Thompson—"so smart, strong, talented, beautiful inside and out, kind, sweet, thoughtful, creative, funny, and witty."

And the list didn't end there. 

"You are the best chef, best party planner, best organizer, and you are the auntie and mommy that everyone wants to be with!!!" the momager added. "You are the one that celebrates all of us. You are the best and most incredible cheerleader to everyone!! You are the life of every party!!! I thank God every day for the blessing of being chosen to be your mommy. I love you more than you will ever know and I cherish and treasure every single moment we get to spend together."

In addition, Kim Kardashian had musical duo Jake & Shelby perform "one of @khloekardashian's favorite songs" in a video message as a surprise, and Kourtney Kardashian marked the occasion with a series of throwbacks on Instagram Stories.

The Lemme mogul—who is expecting a baby boy with husband Travis Barker—shared footage from their time on reality shows Keeping Up With the Kardashians and Kourtney & Khloé Take Miami and finished off her tribute by calling her "an angel." 

To take your own trip down memory lane in honor of Khloe's birthday, keep scrolling.