The mom of three, 36, captioned the paparazzi snapshot as "Bobby." The siblings hold hands in the adorable photo, which appears to have been taken a couple of years ago.
"If only you could see yourself through my eyes!" she captioned a selfie of the twosome. "I'll forever be obsessed with you! My one and only! #MyAce."
Rob is just as supportive of his sisters. Last week, Kris Jenner's only son — who has struggled with his weight and depression for over a year and hasn't filmed Keeping Up With the Kardashians for some time — posted about Kylie Jenner's new lip kit.
"I guess someone is disappointed they didn't get Kylie's lipkit!!!!" Rob captioned a pic of his dog trying to buy the sold-out makeup online. "Don't worry buddy more coming soon!"
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