A five-year-old girl has been hailed a hero for saving her youngest brother as it was revealed the siblings were “trapped inside” the wreckage of the family’s crashed car for two days.

Three surviving children were found with their dead parents in the 4WD in Western Australia’s wheatbelt on Tuesday after failing to return home on Christmas morning.

Police had earlier told media a searching relative discovered the two older children, a girl, 5, and boy, 2, outside the upturned Land Rover Discovery, and the youngest, 1, still buckled into a car seat.

Their parents Jake Day, 28, and Cindy Braddock, 25, were both deceased.

But Mr Day’s cousin Michael Read later told reporters all three children were inside the crumpled wreck during the entire ordeal, and the two-year-old was still strapped in.

“All three kids were trapped inside the car until family members arrived on the crash scene yesterday (Tuesday),” he said.

Mr Read said the couple’s daughter had saved her youngest brother’s life.

“What I’ve gathered is the five-year-old became unstuck in the vehicle, and she then got the one-year-old out of the car seat, then they were stuck in the car for the 55 hours in 30-degree heat,” Mr Read said.

“It would have been hard for the three children to be in the car for that whole time.

“Nobody knows what they went through.

“And if it wasn’t for the five-year-old undoing the buckle of the one-year old’s car seat, he wouldn’t be with us today.”

Three children are now orphans after both parents were killed in the crash. Photo: Facebook

The family had set out from Northam at about 1am on Christmas morning to make the 200km drive back to their home in Kondinin.

The alarm was raised when they failed to make it, but their car was not found until midday Tuesday.

Mr Read said family friends discovered the accident site, where the couple’s daughter and two sons were badly dehydrated inside the station wagon.

In a hint of what could have gone wrong, Mr Read gave a warning to other drivers: “Know what your body limit is, don’t drive tired.”

“If you’re going to want to be somewhere, stay the night at a family’s place. It’s not worth it,” he said.

Police say the car flipped and crashed on the quiet country road, about 10 kilometres from their home town of Kondinin.

Mr Read said miraculously, none of the children had suffered critical injuries and could soon be released from hospital.

“But all the kids are doing fine. They should be out within the next couple of days.”

Mr Read said the family was struggling to come to terms with the tragedy that had orphaned three young children.

“It is hard, having three kids now growing up with nobody. Apart from other family members,” Mr Read said.

“We’re going bit by bit at the moment.”

Jake Day and Cindy Braddock were both killed, but their children survived. Photo: Facebook

‘They looked exhausted’

One of the last people to see the family alive may have been Nathan O’Donnell who works at the petrol station were the family began their drive at Northam.

Mr O’Donnell told the ABC the car drove in at about 1.11am on Christmas morning.

“They then got out, put fuel in, then they came in, they went to the toilet, they came and bought drinks and snacks and stuff for the road,” Mr O’Donnell said.

“They looked very exhausted.

“He told me he was heading to Kondinin and that it was a couple of hours drive.

“He looked exhausted … he didn’t buy a coffee. Then he left, I told him good luck with the long drive.

“Unfortunately, he never made it.”

The wreckage of the Land Rover Discovery in WA’s wheatbelt. Photo: 7News

Shire councillor and local hotel manager Darren Pool said residents were in shock over the “traumatic” incident on the town’s outskirts.

“Being so close to town and no one had noticed it,” he said.

“People have been driving past it for a couple of days. That’s probably the biggest shock for me.”

Mr Pool said Mr Day and Ms Braddock were “battlers” who “did everything for their kids”.

“What we do from here is going to be the hard bit,” he said.

Casey Guyer and Kailee Wallace have set up a Go Fund Me page to help the couple’s family, with more than $6000 raised of the $10,000 goal.

“Devastatingly Jake and Cindy did not survive the accident but an angel was looking over the kids,” they wrote.

“It was a miracle their beautiful babies survived for over two days in the Australian outback.”

-with AAP