Police said there was a “disturbance” at the Ipswich property, moments before it erupted into flames early on Sunday morning.
The bodies of Joseph and Christine Stephan were found side-by-side.
Detective Acting Inspector Heath McQueen described the double fatality as a “very confronting” incident that had left family members “distraught”.
“We’re providing the immediate family members with support,” he said.
Emergency services were forced to break into the Collingwood Park property to extinguish the fire located on the lower level of the residence.
There was no reported history of domestic violence but the detective said the couple’s relationship would “form an integral part of our investigation”.
Neighbours, who were too distraught to speak on camera, said they were well-liked and had two children.
Mr Stephan worked as a real estate agent at the Ray White real estate in nearby Redbank Plains.
Acting Inspector McQueen said the fire “took hold very quickly”.
Police are not looking for a third party, but it could take days to determine the cause of the blaze.
The fire is being treated as suspicious until proven otherwise.
“Extensive damage to the property has been caused, there will be several days of forensic examinations,” Detective Acting Inspector McQueen said.
Autopsies are yet to be carried out to determine the cause of the pair’s deaths.
Detectives are investigating all avenues.