Superintendent of Police (SP) Atul Saxena said that the 16-year-old girl was found in serious condition in Bahjoi area on May 18.
Investigation revealed that the girl was having an affair with her cousin Dharamveer and the couple eloped on May 16 and went to their relatives' house in Pilkhua, he said.
The SP said that while searching for the girl, her brothers Pankaj, Ratan Singh, Devendra and Dharamveer's brother Mukesh along with his aide Jagdish reached Pilkhua.
The four-- Pankaj, Ratan Singh, Devendra and Mukesh brought the couple to Bahjoi where Devendra and Ratan first attempted to strangulate Dharamveer and later threw him infront of a vehicle causing his death, he said.
He said that the girl's brothers and Mukesh have been arrested and the matter was being investigated further.