The bodies of Gouri Bhattacharya and her son, Dipak, were found lying in a pool of blood on the first floor of the house in the city's Behala area, said Kolkata Mayor Sovan Chatterjee
The victims had been killed by slitting their throats.
The bodies of the domestic help and an attendant were lying on the ground floor.
Chatterjee said it was a case of cold-blooded murder.
Dipak Bhattacharya ran a cable TV business and cops will probe to find out if the killing was out of professional rivalry.
Senior police officers had rushed to spot.