The incident took place last night at Sehaltetartoli area when a group of armed assailants barged into the residence of Jagdish Yadav and killed him along with his wife Sumitra Devi and cousin Jaipal Yadav.
Jagdish's mother-in-law Bati Devi was admitted to a hospital with serious injuries, they said.
Police claimed that land dispute could be the cause behind the killing.