Firefighters found the three bodies early Tuesday morning in the burning garage of a home in the small town northeast of Montreal.
Jocelyn Marcoux, 47, and his children, Lindsay and Karen Brillant-Marcoux, are believed to have died in the fire.
Investigators are revealing few details about the incident, including the cause of death. Authorities said they won't confirm the victims' identities until the post-mortem exams are complete.
The family was involved in a protracted custody dispute. Marcoux was due to appear at the Quebec City courthouse the morning firefighters found the bodies in a detached garage behind the family home.
Neighbours reported hearing a noise they described as an explosion early in the morning, just before the fire started.
The bodies were sent to a Montreal laboratory for further examination.
Investigators are still gathering evidence from the scene of the fire.