The incident took place in the Chandwaji area in the wee hours when the victims were on their way to a temple in Samod near here from Alwar, police said.
The deceased have been identified as Rukma Devi(50), Barfi Devi(33) and her husband Pradhan(35) and an eight-year-old boy Sunil, the police said.
The injured were being treated at a government hospital, they added.