Rob Kardashian's weight gain was unwittingly brought up by sister Kim Kardashian after she posted a throwback photo on her Instagram on Monday showing the sock mogul when he was much leaner. Meanwhile, momager Kris Jenner tries to get over divorce rumors by greeting her son a happy birthday.

Kim Kardashian then captioned the Instagram photo with: "Happy Birthday to my baby bro @robkardashian. I love you soooo much!!!!"

According to Daily Mail, the photo was taken two years ago while they attended 1OAK in Las Vegas and the youngest Kardashian was still thin, which the website said only drew attention to Rob Kardashian's recent weight gain.

Rob Karashian, who turned 27, also posted a selfie photo on his own Instagram account showing him wearing a navy blue bandana covering half his face.

The photo was simply captioned: "Happy birthday to me."

Amid the Kris Jenner divorce rumors, the momager also wished her son a happy birthday.

She wrote: "Happy Birthday @robkardashian !!! You are the most amazing young man and the most wonderful son a mom could ever ask for. Continue to Dream Big and Work Hard and Love Completely."

The Instagram post came amid reports that the momager is being very harsh in criticizing Rob Kardashian's weight gain, as tabloids reported that she called him an "embarassment" to the family.

"I am so proud of you, I love and adore you xoxo Mommy," Kris Jenner added.

In the recent episode of "Keeping Up With the Kardashian," Kris Jenner advised Rob Kardashian to watch his weight because his liver is shutting down.

"This is life-threatening at this point. You can only sustain this level of being unhealthy for so long," she said of Rob Kardashian's weight gain.

The sock mogul is also aware that he needs to lose some weight, according to Mirror.

"I've never felt so down depressed in my life. I'm trying to be in the fashion industry and I'm not going to be taken seriously when I'm fifty pounds overweight. It's embarrassing to the family," Rob Kardashian said.