"Happy birthday @robkardashian I would be lost without you!! Thank you for being the best brother anyone could ask for," Khloe, 29, captioned a collage of photos of herself and Rob.
"This year I want to give you the ability to see yourself through my eyes! I want you to own how incredible you are and shine the way you are meant to shine. I love you!!!!"
Rob has been battling weight problems for months and the current season of Keeping Up With The Kardashians has documented his journey trying to get in shape.
"[He] is really depressed," an insider told Us Weekly of his weight struggles. "Rob has a trainer he's supposedly working out with. But Rob rarely shows up for their sessions. He's not losing any weight."