The man, 35, had hanged himself in the family home early Sunday morning. It is thought the two children, an 18-month-old girl and a four-year-old boy, also died by hanging.
The man’s father found the bodies at about 8am yesterday.
The children’s mother was found by police towards midday in Quimper, a town 20 km from Fouesnant. She told the authorities she had left home the night before after an argument with her husband.
Eric Tuffery, the district attorney of Quimper, said: “It seems the two children were hanged. We do not know yet if they were sleeping before.”
The three bodies are due for autopsy in Brest today or tomorrow.
Tuffery is treating the case as a double homicide and suicide following a conjugal separation.
A neighbour told local paper Ouest-France: “Things were not running smoothly (between the husband and wife). They had argued several timhes before.
“And she (the mother) wasn’t there last night. He must have just lost it.”