The parents arrested last year on suspicion of murdering their son 28 years ago made an emotional TV appeal shortly after he vanished.
Steven Clark was last seen on December 28, 1992, in Saltburn-by-the-Sea, North Yorkshire.
Former police officers Charles and Doris Clarke were quizzed last September after a cold case review of the 23-year-old’s disappearance.
They both categorically deny any wrongdoing and have since been released under investigation.
In the film she says: “We torture ourselves, wondering where he is, and we think every day, where is he? Is he safe?”
Dad Charles wonders if Steven “wanted to prove he could live by himself” because of his disability following a car accident when he was two years old.
Sister Vicky adds: “We really love him and miss him.”
Last week, police released TV footage of Steven, who had a damaged left arm, a damaged leg and a distinctive limp.
It was first aired in 1993 on an ITV show about missing people with Alastair Stewart and Fiona Foster.
Doris and Charles still live in Marske-by-the-Sea, in the family home which they shared with Steven at the time of his disappearance a few miles away.
Det Chief Insp Shaun Page, of Cleveland Police, said the film was being re-released in the hope of finding new witnesses.
The Mirror revealed last month Doris, 82, and Charles, 78, are taking part in a new ITV documentary about the case.