Russell Martin has been missing from his home in Stawell, Victoria, since January 1977.

Mrs Roberts said she thinks about her brother every day.

"Not a day goes by that I don't think about where he is," she said. "It's not a matter of who or what happened. We don't have time for that anymore.

"For me, I just want to find my brother so I can lay him to rest before I die."

Mrs Roberts said she had never given up hope.

"I've been down so many paths trying to find more information but doors have just kept closing on me," she said.

"Despite how long it's been, there could be some small piece of information that could help piece the puzzle together."

Mrs Roberts said she lies awake at night wondering about her brother's fate.

"Those questions are there every night," she said. "Was he alive when something happened to him? Did he suffer?

"I've gone to enormous lengths to find answers."

Mrs Roberts is certain someone somewhere knows something about what happened to Russell, a woodcutter, then aged 31.

"It's been a long and harrowing lifetime," she said. "There have been lots and lots of tears. Deep down in my heart I know there has to be more information out there."

An inquest into Mr Martin's disappearance was held in 2002, 25 years after he was first reported missing.

After the inquest, Mrs Roberts said the case just died.

"After watching ABC one night I saw Missing Persons Advocacy Network CEO Loren O'Keeffe on a show," she said.

"I decided to write to her and ask for help. Two years later here we are, giving it one last shot."

That came in the form of a popular true crime podcast - Casefile: True Crime series

"I just want anyone with any information to speak out," she said. "Now is the right time. Maybe it might not have been the right time before for whatever reason - I don't care about any of that.

"Every human deserves to be laid to rest and that's what I want for my brother.

"We're not going to get there unless someone comes forward."

If anyone has any information about Russell Martin they are encouraged to contact Crimestoppers on 1800 333 000.