The devastated parents of two young children killed when a car ploughed into their pram wept at the siblings' funeral as they thanked the community for the outpouring of sympathy. 

Vundy Tha and Sok Ram paid tribute to Katherine, 5 and Harry, 1, at the family Buddhist ceremony in Fairfield, Western Sydney, on Tuesday, days after an SUV struck them when they crossed the road in Cabramatta. 

Ms Ram called her daughter her 'angel' at the service and remembered her kind and caring nature. 

'I just want them back. She had such a good heart,' she said. 

'Everyone would say what a kind heart she had. 

'My heart is broken, I still can't believe she's gone.' 

Ms Ram also said she loved both school and sport. 

'She was so smart and happy, loved school and she always liked to be first in the line for school,' she said.

Mr Tha said 'she loved to be number one'.

'I would say to her ''you don't always have to be the best,'' but she still wanted to be number one.' 

Seven Buddhist monks performed chants at the initial ceremony as the parents walked around the open coffins and lit candles, The Daily Telegraph reported.

Ms Ram then recalled how the siblings had been in her dreams since their passing.  

'Every night they say ''I love you mummy'',' she said.

Mr Tha said he was still trying to trying to process the awful tragedy. 

'He (Harry) had just started walking (and was) always causing mess,' he said. 

'We still can't believe what's happened. 

'We only had two children.'

After the ceremony, the coffins were transported past the family's house to the cremation at Forest Lawn Memorial Gardens in Leppington. 

Family and friends, members of Sydney's Cambodian community and Katherine's Cabramatta West Public School teachers were in attendance. 

Family friend Patrick Te previously told Daily Mail that Sok was crossing the road at the corner of Gilbert and Joseph streets after walking back to their car following the school pickup when the tragedy unfolded. 

'She saw the driver stop and thought he was going to give way, but then he hit them and kept going,' he said.

'She was knocking on the window trying to get him to stop as they were dragged along the road.'

He said Katherine was showing her mother a school award just moments before.  

Mr Te set up a GoFundMe page to help support the family which has raised more than $400,000.

Many people also used the platform to send their condolences.  

'May your precious babies rest peacefully in heaven and I also hope you find peace and strength during this incredibly difficult time,' one said. 

'My deepest condolences to your family during this unimaginable time. My thoughts and prayers are with you and your loved ones as you navigate this devastating loss,' a second said. 

'Although we do not know you personally, we are absolutely devastated by this heartbreaking news. Our hearts ache for you and for the unimaginable loss you are enduring,' a third said. 

Fairfield City Police Acting Superintendent Timothy Calman said members of the public played a 'phenomenal' role in attempting to save the children. 

'The community involved here this afternoon was … I can only say it's phenomenal,' he said.

'We've had a number of motorists that actually stopped, and collectively have moved the vehicle onto its side, tipped the car over, in order to get one of the children from underneath the vehicle.

'Other bystanders have assisted with CPR to assist the children and the children's mother.'