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.