Rob Kardashian seems to be the "underdog" of the famous Kardashian clan. While the family was vacationing in Thailand, Rob continued his struggle with his weight gain back home. The sock maker took to his twitter to express his sadness and pain over ex-girlfriend Rita Ora and his overall depression.

"No one will ever understand how much it hurts," the 27-year-old Kardashian tweeted a few hours past midnight. We suspect that this tweet might have something to do with ex-girlfriend Rita Ora making headlines while gushing over new boyfriend Calvin Harris. Rita told Elle U.K. that "she'd never been in love before Harris"... ouch. As we remember, Rob and Rita had an ugly and messy split after Rob accused her of cheating on him with 20 other men back in 2012. So, is he still hung up on a girl who broke his heart?

The Keeping Up With The Kardashians star's struggle with his weight seems to be affecting his mood to the point that everything affects him deeply. An insider told Us that Rob is "really depressed," adding that he "rarely shows up" for his personal training sessions and the "the family is very concerned about him." So, was leaving him behind while they all went to Thailand a good idea? On April 2, Kris Jenner posted a photo of a beautiful scenery with the caption "Gorgeous Thailand," with shout out to Brandon and Brody Jenner, Brandon's wife Leah, Bruce Jenner and daughters Kim, Khloé, Kendall and Kylie hashtagging "#family #love #memories".

Well, Rob is an adult and maybe Kris Jenner's tough parenting with her only son is meant to make Rob stop feeling sorry for himself. Do you think Rob's family should pay a little more attention to his depression? Who do you think the tweet was about?

Click here to check out Rob's Twitter page.