The family of a five-year-old who survived a Hunter Valley car crash, but lost a father and grandfather, says the boy is "understandably shaken".

The boy was found wandering around with a broken arm after the crash, which also took the life of local real estate agent, Adam O'Regan, 48.

The boy's family said they requested "peace and privacy at this incredibly difficult time for our family".

"Yesterday our family suddenly lost a father and a grandfather," the statement said.

"Our son, who thankfully sustained non-life threatening injuries, is understandably shaken and it is our family's number one priority to be there and care for him as he recovers.

"As we support our son through his recovery we are also grieving the loss of two loved ones."

The 5-year-old boy was taken to John Hunter Hospital in Newcastle after being found on the property. ( ABC News )

It is understood the boy and his family were visiting from their Sydney home to look at properties in the Gundy area, east of Scone.

When the car did not return, the real estate agency sent out a car to find the group.

They found the injured boy wandering and he led them back to the crash site where the car had rolled 400 metres down a steep embankment.

Men may not have been wearing seat belts: police

Acting Superintendent Guy Guiana said the men, including the boy's father, aged 42, and grandfather, aged 75, were thrown from the car and were found dead at the scene.

"It would appear that the younger male, the son, was killed pretty much instantly, and we do believe that his father was alive for some time and may have made his way to his son before he died," he said.

He said it was unclear if the men were wearing seat beats as they toured the rural property.

Acting Superintendent Guiana said initial investigations suggest the boy was still in the vehicle when it came to a stop, but the men were not.

"All I can say for certain is they were ejected from the vehicle," he said.

"It may be the case that they weren't wearing seat belts. If that is the case that's obviously fairly tragic."

Acting Superintendent Guiana was asked if a mobile phone call for help from the boy cut out due to poor phone reception.

"I can't confirm that," he said.

"I can say that there's intermittent phone reception in the area depending on whereabouts you are."

The boy was airlifted to the Scone Hospital before being taken by ambulance to the John Hunter Hospital in Newcastle, where he remains in a stable condition.

Police will prepare a report for the coroner.