Brothers nine, 12 killed in Dubbo crash

A double tragedy has struck a family travelling in NSW's Orana region in the early hours of the morning.

Two brothers, aged 9 and 12, died when their family's 4WD crashed with a B-double truck on the Newell Highway near Dubbo about 3.30am on Saturday.

The boys' parents survived the collision along with their four-year-old brother who police initially believed was aged five.

The older siblings were found dead at the scene. The youngest boy was airlifted to Westmead Children's Hospital in Sydney in a serious condition with internal injuries.

The parents were treated at the scene for minor injuries.

The male truck driver has also been airlifted to hospital with serious injuries.

The Newell Highway has reopened after being closed in both directions following the crash.