Rob Kardashian's family are ''worried sick'' about him.

The 28-year-old sock designer is said to have alarmed his relatives with his rapid weight gain and depression, with the Kardashian and Jenner families becoming increasingly worried about his lifestyle.

A source said: ''Rob has extreme social anxiety, is very unhealthy and just isn't doing anything to get back on his feet.

''The whole Kardashian and Jenner family is worried sick about him but they just don't know what to do.''

However, his mother Kris Jenner and sisters Kim, Kourtney and Khloe Kardashian are believed to be finding it ''virtually impossible'' to help the star as he is refusing any kind of support.

The insider added to HollywoodLife.com: ''He refuses to get therapy or to go get help. He has his own money still as he spends very little

''They feel like they have tried everything but until Rob wants help it's virtually impossible for them to give him help.''

Meanwhile, a source previously claimed that Kris had banned Rob from appearing in any episodes of their hit E! reality show 'Keeping Up With The Kardashians' until he got better.

They said: ''Kris doesn't want Rob on the show when he is emotionally unstable.''