Kylie Jenner on Rob Kardashian: He's 'My Best Friend, My Heart'

Instagram

What's going on with Rob Kardashian?

Kylie Jenner is clearly feeling sentimental about her older brother Rob Kardashian.

The Kardashian family has made no secret about 28-year-old Rob's reported issues of depression and his weight battle, and on Tuesday, 17-year-old Kylie reached out to him via her Instagram.

"My best friend, my heart, my brother," she wrote alongside a close-up of Rob on the beach.

PHOTOS: 7 Celebrity Sibling Feuds

Kylie's not the only member of the family keeping the former reality star in her thoughts. Despite some obvious fighting between sister Kim and Rob -- Rob didn't attend her 2014 nuptials to Kanye West, and he took to Instagram to call her "the b**ch from Gone Girl" in March -- she carried a cardboard cutout of Rob's face during her trip to Armenia earlier this month. 

Getty Images

"He obviously has some kind of depression," Kim said in a recent intense episode of Keeping Up With the Kardashians. "He is the king of excuses ... I'm the only one that's really tough with him so he probably avoids me the most."

Meanwhile, Kris Jenner has said that if she doesn't do something drastic for her son, "he's gonna die."

"He was always someone who was very athletic growing up, and he's gained over 100 pounds in the last year," she tearfully told a life coach during the episode. "He doesn't want to participate. He doesn't go out of the house. He's missed Christmas, he's missed Kim's wedding."

Aside from posting then deleting his eyebrow-raising Gone Girl Instagram, Rob has clearly been staying out of the spotlight. He follows zero people on his official Instagram, and his last tweet was a retweet of Diddy's March 31st post reading, "Pay close attention to the people who don't clap when you win."

Whatever his current issues may be, Rob was definitely once close to Kylie. Kylie has modeled for his line Arthur George, and frequently attended events with her big bro. Check out Rob with Kendall and Kylie at KIIS FM's Wango Tango concert in May 2010.

Getty Images

VIDEO: Kylie Jenner Responds to Disturbing 'Kylie Jenner Challenge'

Watch the video below to see Kris break down into tears over Rob's reported troubles.