A Fijian teenager injured in a car crash that claimed the lives of an elderly couple in NSW is no longer in a critical condition.

The 14-year-old was one of five family members taken to hospital following the single-vehicle crash 6km north of Holbrook in southern NSW on Wednesday.

A husband and wife, both aged 70 and visiting from Fiji, also died when the seven-seater Nissan Patrol left the Hume Highway and rolled about 6.55am (AEDT).

The teenager suffered head injuries in the accident, and was airlifted to Canberra Hospital in a critical condition.

His condition improved overnight and he's now in a stable condition, an ACT health spokesman said.

The crash survivors are from Chisholm in the ACT and all are from the same Fijian family.