Police say a neighbour called them about a disturbance just before 1 p.m. MT.
EMS was called but both were pronounced dead at the scene.
The child is believed to be about eight years old.
Calgary's homicide and major crimes units are investigating.
Neighbours say they are shocked and saddened by the news, but knew little about the family that lived in the house.
Police say they believe a husband and wife lived there with their children. The man and other children have been located and are safe, they say.
In relation to the case, police say RCMP took a man in for questioning. He had been on a highway near Didsbury, about an hour's drive north of Calgary.
Autopsies are expected to be performed Friday.Suggest a correction