The boys' mother, who is in her 30s, and a newborn who is only a few days old were intoxicated by the smoke and rushed to hospital in critical condition.
The Sûreté du Québec said the fire started around 6:30 p.m. on the second floor of a four-unit apartment building on des Écoles Street.
Investigators are on the scene trying to determine the cause of the fire.
