The incident occurred on the intervening night of Wednesday and Thursday when Ramkishan, a farmer, was allegedly performing the superstitious ritual, Station House Officer, Gogamedi police station, Naresh Kumar said.
He threw his son, Sunil, on the ground killing him on the spot. When his wife, Rachna (27), came to rescue the child, Sunil hit her repeatedly with a hammer and bludgeoned her to death, the SHO said.
Police were informed after locals discovered Rachna's body yesterday.
The bodies were handed over to family members after postmortem yesterday.