The deceased, identified as Kuldeep Singh suspected his wife Reena Kumari (25) of having an illicit relation with his cousin Balwinder Singh (29), they said.
According to the police, following an altercation between Kuldeep and Balwinder yesterday, the latter allegedly hit Kuldeep with a brick which led to his death on the spot.
Upon hearing about Kuldeep's death, Reena allegedly committed suicide by consuming poison, SHO Mukerian Police Station Jagdish Singh said.
A murder case has been registered and police have launched a manhunt for Balwinder, who is absconding since the incident, the SHO said.