Although Khloe Kardashian recently admitted she's lost her patience for Rob Kardashian -- especially this year -- it's safe to say the bond between the close siblings is unbreakable.
Khloe took to Instagram on Monday to share a heartfelt message to her younger brother, posting a throwback photo of Rob kissing her on the head.
"If only you could see yourself through my eyes!" Khloe wrote. "I'll forever be obsessed with you! My one and only! #MyAce"
WATCH: Khloe Kardashian Says Rob Kardashian Is 'Wasting His Life'
Rob, 28, has struggled with depression and weight issues for the past two years. In an April episode of Keeping Up With the Kardashians, his mother, Kris Jenner, said he gained 100 pounds in the last year.
"I've been working on my patience," Khloe, 31, told People in October about Rob. "I've been really trying. But I have my moments and I do snap. I've offered to get a chef, I'm like, 'What's your excuse?' But it's not just that. I can't win life for Rob. I have to wait until [he's] ready to do it for himself."
"Rob is such a great guy," she added. "He's charming, charismatic, everything. That's what's so infuriating. I'm like, 'Where is your will to live life? Let's be around people!'"
Rob currently lives with Khloe in her Calabasas, California, home and has been keeping a low profile from the public for more than a year. Earlier this month, Kris revealed that her only son didn't spend Thanksgiving with his famous family.
"He lives with Khloe [who hosted the holiday dinner this year], so he was around, and then went over to a buddy's house," Kris told Maria Menounos on her Sirius XM radio show, Conversations With Maria. "He's doing alright, he's doing his best. "He's working on himself."
"He's gonna be OK," she continued. "He's not as into being on camera as the rest of us."
WATCH: Rob Kardashian Posts Rare Instagram for Kylie Jenner's Lip Kit, but Not Kim Kardashian's New Baby
Apparently, he's not that into social media either. Rob has been largely absent from both Twitter and Instagram this year, though he did take some time out last week to promote his younger sister Kylie Jenner's sold-out lip kit. Curiously, he made no mention of a much more significant event that happened in the Kardashian family, although the news broke the same day -- Kim Kardashian giving birth to her second child with husband Kanye West.