Former Home and Away actress fighting for life after tragic Boxing Day crash.

Relatives have rushed to the bedsides of two sisters critically injured in a fiery crash on the NSW south coast after their parents died in a burning car.

Former Home and Away actress, Jessica Falkholt, 29, and sister, Annabelle, 21, remain in critical conditions following the head-on Boxing Day crash near Ulladulla that killed their parents.

Police believe a four-wheel-drive crossed the road and collided with the car carrying the family.

Witnesses and police pulled the sisters from the wreckage as the vehicles were engulfed in flames.

home and away actress crash

The remains of the 4WD's driver and the Falkholt's parents in the car were so badly burned it could take weeks to formally identify them, AAP understands.

The girls were airlifted to Liverpool and St George hospitals.

Police visited the family's home in Ryde but, after finding no one at home, tracked down extended family members.

"Sadly those family members are travelling to the St George and Liverpool Hospitals to engage with their loved ones who are very much in a critical condition at this time," Highway Patrol Chief Inspector Phil Brooks told reporters in Sydney on Wednesday.

Jessica played the role of Hope Morrison on the favourite Australian TV series in 2016.