Police later found that three youths, who are suspected to have been be in an inebriated condition, were in the car when the mishap occurred last night.
Ms Kokila S Kumar, a councillor of Kollam Corporation, died on the spot while her father Mr Sunil Kumar, 50, succumbed at a private hospital in neighbouring Thiruvananthapuram in the wee hours today.
The accident occurred when they were returning home after attending an Onam celebration organised by a local residents association.
The car was cruising at a high speed when it hit the two-wheeler from the rear and halted briefly before speeding away, police said.
Police have identified the owner of the car, which was found abandoned at a house at near Sakathikulagara.
Police said a search is on for the three youths.