The man and woman, their two sons and a teenage friend were in the car when it rolled on Gooburrum Road at Welcome Creek, about 12 kilometres north of Bundaberg.
The parents, both aged 37, died in the crash while their five-year-old son and his 17-year-old brother suffered minor injuries, Queensland Ambulance Service (QAS) said.
The teenage boy’s 15-year-old girlfriend suffered serious head, chest and limb injuries after being thrown up to 30 metres from the car.
QAS spokesman Martin Kelly said the boys’ mother was also thrown from the vehicle.
“These people were just a couple of hundred metres from their home when it would appear that their vehicle has left the road and rolled over,” he said.
“One of the deceased was thrown from the vehicle and a seriously injured teenager – she was thrown some 20 to 30 metres from the vehicle and has quite significant head, chest and limb injuries.”
He said it would appear there were no witnesses to the crash.
“It’s quite a distressing scene,” he said.
“It was on a road that was only single lane and has gravel either side, on a bend, with a creek crossing.
“There were some people who were at a house very nearby the incident and they came out and rendered some wonderful assistance to the people that were injured … until the ambulance and other emergency services arrived.”
The three children were taken to Bundaberg hospital for treatment.