The accused, Ganesh Kaurav, worked as a watchman at the bungalow of a retired IAS officer Ashok Sahay and also stayed there with his family of five, police said.
Kaurav suspected his wife Rajkumari of having an affair with one Raju Rajak.
Last night, Raju came to the watchman's residence where both consumed liquor and went to sleep. Late in the night, Kaurav picked up a wooden stick and started beating his wife and Raju, Superintendent of Police (SP) Anshuman Singh said.
Kaurav's eldest daughter, who is 14, told police that when she and her siblings tried to protect their mother, they too were thrashed by their father, Singh said.
Rajkumari and Raju were rushed to a nearby hospital where they died during treatment. The watchman has been booked for murder and efforts were on to nab him, he added.