The slaying of multi-millionaire Herman Rockefeller has been linked to Melbourne's underground swingers' network.

The body of the 52-year-old was found in a junk-strewn suburban backyard eight days after he was reported missing.

While a missing person's investigation into his business activities across Australia and New Zealand turned up nothing unusual, it's believed detectives uncovered details of the Harvard graduate's secret double life.

Police discovered Mr Rockefeller had been using erotic websites to find partners within Melbourne's swingers' network, sources close to the family have told AAP.

His relatives have been told of the development, with his brother Robert saying on Saturday that they were "devastated by Herman's loss and deeply shocked by the circumstances surrounding his death".

The development allegedly led police to a Hadfield home near Melbourne Airport, where Mr Rockefeller had met two residents who are now charged with his murder.

Mario Schembri, 57, of Wallan, and Bernadette Denny, 41, of Hadfield, will appear in court on Monday.

An out-of-sessions court hearing has been told Mr Rockefeller was killed at their home within hours of his return from an interstate business trip.

The property investor was last seen on CCTV footage at Melbourne Airport after 9pm (AEDT) on January 21.

Both Schembri and Denny have admitted to being involved in a fight with Mr Rockefeller, which led to his death, and have told police they assisted or had knowledge of the disposal of his body, the court heard.

Police were taken to a home in the neighbouring suburb of Glenroy on Friday evening and there they found human remains in a backyard cluttered with car and boat parts.

Neighbours said homicide detectives questioned them about any unusual activity in the area.

"They asked whether we had seen fire or smelled fire," Marika Williams, 33, told AAP.

"And we did mention that on Australia Day we had smelled something about four o'clock in the afternoon."

Forensic testing is under way to confirm if the human remains are those of Mr Rockefeller, but police have already told his family that they are those of their missing relative.

Mr Rockefeller allegedly died in a run-down home a world apart from his million-dollar lifestyle in East Malvern where he enjoyed a mortgage-free mansion, a home office and two teenage children - one who was recently accepted into medical school.

He could have retired at 40 after holding senior business positions with New Zealand's Brierley Investments and the Pratt family's Visy empire in Melbourne, but he kept working to keep busy, making millions off property investments in Tasmania, Victoria and NSW.

Friends say the American-born businessman and avid marathon runner had no hints of a secret life and was a devoted family man.

His wife heard virtually every phone call he made because of their shared office.

When Mr Rockefeller vanished, police considered a vast range of theories from kidnapping to a mid-life crisis as possible explanations.

Detectives followed those theories for days as unconfirmed sightings poured in across Victoria. All of those sightings have now been discounted.

After his 2007 Toyota Prius was found abandoned in rural Victoria four days after his last confirmed sighting his family stopped giving media interviews. Homicide detectives then became more involved in the investigation.

Police have never said what they found in the car.