Rob Kardashian is reportedly "out of control".

Rob Kardashian

Rob Kardashian

The 28-year-old reality television star has been battling with his weight over the past few years and has become something of a recluse, and now his family are said to be "terrified" that he will soon be beyond help.

A source said: "Rob has gone off the rails again. He is, once again, out of control."

Insiders added that the birth of Rob's sister Kim Kardashian's son Saint has contributed to his setback, as he allegedly feels that all the focus is on his older sibling.

The source added to RadarOnline.com: "He was doing so well for a minute but is now off the radar again and he seems to feel neglected because the entire family is focused on Kim, as usual.

"Nobody knows what to do anymore because Rob will not even leave the house. He seems really bad off and everyone is really worried."

Rob's stepmother Caitlyn Jenner is said to be keen for him to try rehab, as she feels it could be the answer to his problems.

Khloé Kardashian recently sparked concern with a post on her Instagram page, showing a throwback picture of herself with Rob.

She captioned the snap: "If only you could see yourself through my eyes! I'll forever be obsessed with you! My one and only! #MyAce."