The incident took place last evening at Nana Jadara village of Mahuva taluka in Bhavnagar, they said.
Investigation by Mahuva police has revealed that a verbal spat between two women of a family ended in the murder of Pravin Velari (55) and his daughter Vanita (22).
Pravin's injured son Ashwin (18) and wife Manjula (48) have been admitted to a hospital in Bhavnagar, said Police Inspector of Mahuva A H Rajput.
"All the accused are distant relatives of Pravin and live near his house. Ashwin claimed that Vanita and her aunt Sarla had a quarrel over a petty issue. After which Sarla instigated her husband Himmat about Vanita," said Rajput.
Out of the grudge, Himmat and Pankaj stabbed Vanita, Pravin, Ashwin and Manjula with knife and fled from the spot, said police.
"Due to fatal injuries, Pravin and his daughter died on the spot. Ashwin and his mother Manjula are now being treated in Bhavnagar based hospital. We have taken Ashwin's complaint and started our investigation. No arrests have been made yet," added Rajput.