Rob Kardashian makes social media return with rare message about Khloe Kardashian

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.