The man's wife, 80, and their other son, 49, are in stable condition in hospital.
The fire at 32 Charrington Cres., near Jane Street and Sheppard Avenue West, broke out just after midnight.
Fire crews found the house engulfed in heavy smoke and flames.
“When the first crews showed up, the fire was well on its way at the rear of the house," said Tony Belevance, the Toronto fire department's platoon chief. "One of the occupants was at the front and he informed them that there was possibly three members of the family inside."
Firefighters pulled a woman from the building but were unable to complete their search due to heavy flames.
The fire broke through the main floor from the basement, causing the back half of the basement to collapse.
Crews were eventually able to get in and locate one body. The second victim is believed to be buried in the rubble of the collapsed basement.
Two firefighters were also injured and taken to hospital with minor smoke inhalation.
Cause of the fire is unknown. The Office of the Ontario Fire Marshal has been called in to investigate.
Neighbours tell CBC News the family has lived on the street for decades.