80-year-old Hukum Chand Jain, his son Rakesh Jain, 50, and daughter-in-law Vijaya, 45, were killed when their car collided with a state transport bus as they were on their way to New Delhi railway station, police said.
Rakesh's brother Mukesh, who was driving the car, managed to escape unhurt along with another brother, Virender.
A cousin of theirs, Parag, however, has been admitted to hospital where his condition is said to be critical, police added.
According to police, the accident took place at around 5.30 AM on Sunday.
The driver of the bus, which plies between Jalandhar and IGI airport, has been identified as 38-year-old Jagtaar Singh of Gurdaspur in Punjab, police, meanwhile, said.