The sister of a person-of-interest in the case of a missing couple from St. Albert says her brother has nothing to do with the disappearance of Lyle and Marie McCann.

Nearly a month has gone and there is still no sign of the couple.

The couple left for Chilliwack, B.C. on July 3, 2010 and have not been seen or heard from since.

Police are still trying to piece together clues that may lead them to the missing couple.

The McCann's burned-out motor home was found on July 5th near the Minnow Lake campground approximately 35 kilometres southeast of Edson. On July 16th, their green Hyundai SUV was located deep in the bush about 30 kilometres east of Edson near Carrot Creek.

Travis Vader was arrested last Monday on charges unrelated to the couple's disappearance. Vader was picked up by officers at a rural residence near Niton Junction. 

RCMP believe Vader either knows something about the case or is involved in the disappearance of the St. Albert couple.

But his sister says she doesn't believe her brother is capable of hurting anyone. Bobbi-Jo Vader admits her brother has been dealing with serious drug problems in recent years, and says she is glad he is in custody getting some help.

The man's sister is standing by her brother.

"He would never harm or do anything to an innocent person. Travis is not like that whatsoever. So I believe in my heart that he had nothing to do with the missing couple," she said.

Bobbi-Jo says her brother showed up at her house on July 4th -- one day before the McCann's burned-out RV was found -- to rest and grab a meal. She would not say what vehicle Vader was driving when he showed up at her house but says it wasn't the green Hyundai SUV the missing couple was towing behind their RV.

"He had been running around in the bushes and just needed to eat and sleep," she said.

The couple's son, Bret McCann, says he has his doubts that Vader doesn't know more than he is telling.

"Well I don't know, I mean the police have described him as a person of interest," he said.

The McCann family still believes police are on the right track. Bret says they recently met with Mounties and were told the investigation is going "favourably."

"We don't like to contemplate the other scenarios and we're optimistic that my parents will be found and will be found safe."

RCMP say they are still hopeful Vader will open up to officers.

"We believe he either has information or may have some involvement in the McCann investigation," said Sgt. Patrick Webb with the RCMP.

Bobbi-Jo says she does hope police get the answers they are looking for.

"I really hope they find their parents...from the bottom of my heart."

Vader did have a court date scheduled for Tuesday, but it was on a unrelated matter. His case of allegedly breaching a recognizance order by drinking alcohol has been put over to next month.

With files from Bill Fortier