The mishap occurred at Oonjalampatti junction, when the family was returning to Pollachi after a pilgrimage to Rameswaram and Tiruchendur, police said.
The driver allegedly lost control of the car and rammed it into the rear side of a lorry, they said.
In the impact, Nataraj (70), Thirumurugan (42) Jayalakshmi (36), Anandhakrishnan (40) and Srinidhi (10) died on the spot.
Three others Priya (35), Charudeepa (10) and Darshan (8), who were seriously injured were admitted to the Government Hospital here, where their condition is said to be serious, police said adding a case has been registered.