Tragedy as parents and their three-year-old son are killed in highway smash - leaving five-year-old daughter to grow up without them

A couple and their three-year-old boy have been identified as the victims in a catastrophic car collision in Victoria.

Krishna and Sapana Bhandari, aged 41 and 31, and their son, Ruben, died at the scene of a smash on Eurambeen-Streatham Rd outside of Stoneleigh, about 200km west of Melbourne, about 9.30am on Tuesday.

They leave behind a five-year-old daughter, Reuben's sister.

It's understood the family were at the intersection with Mount William Rd when their vehicle collided with a truck.

President of the Geelong Nepalese Association, Niraj Karanjeet, said the tight-knit community was in 'deep mourning' over the tragedy.

'This has been very heartbreaking and has hit the community hard,' Mr Karanjeet told the Geelong Advertiser.

'It is the worst thing to happen to us in the 15 to 17 years since we formed.'

Victoria Police on Tuesday stated a woman had been trapped in the backseat of the family's car and was airlifted to the Alfred Hospital with life-altering injuries.

The family were known throughout the Armstrong Creek community, 11km south of Geelong, and 'embodied a wonderful community spirit' since migrating in 2017.

The family's relatives in Nepal have been informed of their deaths by the Nepalese Consulate.

Mr Karanjeet identified the other woman in the car as Mrs Bhandari's elderly mother and said her condition had stabilised.

'They were incredibly caring. I also pray for the speedy recovery of the injured grandmother,' Mr Karanjeet said.

The Geelong Nepalese Association also shared a touching tribute to the couple and their son online.

'Words cannot express the pain and sorrow we feel at this heartbreaking moment,' the statement read.

'We extend our deepest condolences and prayers to their family and relatives.

'May their beautiful souls rest in eternal peace, and may their loved ones find strength and comfort during this unimaginable time.'

Major crash detectives have launched an investigation into the crash.

It has been reported the family's vehicle could have missed a stop sign and collided with a B-double truck.

The truck driver is assisting police with inquiries.