Khloé Kardashian infuriated by brother

The 'Keeping Up with the Kardashians' star's younger brother retreated from the public eye almost 18 months ago amid reports he is battling severe depression after gaining more than 100 pounds, and she admits she occasionally loses her patience with him.

Asked about the 28-year-old sock designer, the 31-year-old beauty said: "Rob is such a great guy. 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!' "

But Khloé insists she understands that she needs to wait until Rob, who lives with her in Calabasas, California, is ready to seek help. 

She told PEOPLE magazine: "I've been working on my patience. 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." 

Khloé believes Rob's suffering has a lot to do with the fact he "doesn't have a father figure in his life," as their dad Robert Kardashian died in 2003 from cancer and their mother Kris Jenner's ex-spouse Caitlyn Jenner transitioned into a woman in May and was going through her "own things that none of us understood at the time."

Rob once had a close relationship with Khloé's estranged husband Lamar Odom, whom she split from in December 2013, but she added: "Once Lamar left--and it's not Lamar's fault at all--I think Rob didn't know where to go. He was like, 'I don't have guidance anymore.' "

She added: "[Rob] has to figure it out for himself. And he has so many people who want to help him."