"His family will continue to push for him to get help until he does." a source tells PEOPLE of Kris Jenner's only son
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Rob Kardashian‘s family thinks he needs help.

“He’s sad, he’s bitter, he’s single. He is very depressed and has been [for a while],” a source tells PEOPLE of Kris Jenner‘s only son.

Rob raised eyebrows Sunday after posting an Instagram photo comparing his sister Kim to fictional psychopath Amy Dunne from Gone Girl, but he actually has a long history of emotional outbursts, which has been documented on their E! reality show Keeping Up with the Kardashians as far back as three years ago.

“It’s really hard for him that his sisters are so public and he looks like the shut-in,” the source says of Rob, who has watched his sisters’ business ventures succeed while his own sock line fizzled.

Rob has also faced scrutiny about his weight – which led him to abruptly cancel his plans to attend Kim’s May wedding – and allegations of drug use after pictures surfaced in June showing him surrounded by paraphernalia associated with the cough syrup and soda blend known as “sizzurp.”

“The attitude has always been that when Rob gets his act together, starts working out and loses weight, everything will be good and he will be happy,” says a production source on the family’s reality show. “But behind the weight gain is this very unhealthy mental state that he keeps struggling with.”

The production source says the family has attempted multiple interventions – to no avail.

“He is very against therapy and any kind of rehab,” says the production source. “But his family will continue to push for him to get help until he does.”

For more on Rob Kardashian’s struggles pick up the latest issue of PEOPLE, on newsstands Friday

Rob Kardashian Is ‘Depressed and a Bit Off’ Lately: Source