Ranchi: Police have arrested a man, along with his wife, for allegedly poisoning his cousin brother in the Lodma village under the Tamar police station over an alleged extramarital affair, police said on Tuesday. The accused were identified as Baldeo Machhua (38) and his wife Geeta Devi (35). They killed Shankar Nayak (22) after Baldeo found out about the affair Geeta was having with his cousin brother, the police said.Addressing a press conference on Tuesday, Bundo sub-divisional police officer Om Prakash said both accused were arrested from their home at Lodhma late on Monday.Prakash said, “Shankar had lost his parents three years ago, and Geeta started taking care of his household affairs since then. Later, she developed an extramarital affair with him. When Shankar met a girl recently, he wanted marry her, but Geeta got angry as she did not want him to leave her.”She then conspired with her husband to poison Shankar to death by mixing insecticide with tea. Soon after the victim drank the tea, his health condition turned serious. Though he was rushed to the Tata Medical Hospital (TMH) in Jamshedpur, he succumbed on the way.Police have registered an FIR against the couple and their minor daughter Sohini Kumari, based on a complaint from Shankar’s brother, Sukra Nayak. Sohini, being a minor, has not been taken into custody, police sources said.It may be stated here that another couple were also arrested for beheading a man, who was having an illicit relationship with the wife, in the Mandar area of Ranchi district on Monday.