The deceased were identified as Shahidul Islam, member of Chandipur union parishad under No 2 ward and Moukli Begum, 48.
Quoting local people, Md Maruf Hossain, officer-in-charge of Indurkani Police Station, said hearing screams from the house of Shahidul local people rushed over there and found Shahidul and his sister-in-law lying in a pool of blood near a pond.
His wife, Rehena Begum, was found injured and she was taken to Pirojpur district hospital.
Rehena said a group of miscreants, led by one Yunus, swooped on their house and stabbed Shahidul and Moukli indiscriminately.
The miscreants also hit her with a sharp weapon, said Rehana.
There had been long standing enmity between Shahidul and Yunus over family feud, she said.
However, police suspected that the incident occurred due to extramarital affair involving a neighboring household.
Nasrin Zahan, additional superintendent of Pirojpur district police, said the murder is believed to have occurred due to political and family disputes, reports UNB.
Efforts are underway to arrest those involved in the incident, she said.