Tony Abbott's promise to shirt-front Vladimir Putin and the arguments over the leader's words has a surreal disconnection for the Old Toongabbie couple.

On Monday they finally received the ashes of their 25-year-old son Jack, who had been killed in the Ukraine disaster. And while the politicians argue over who will do what at the G20 meeting in Brisbane, the O'Briens are left feeling bewildered, angry  and powerless.

They know revenge would be futile and believe it would only add to the violence and callous indifference that cost their son's life. And confronting Mr Putin won't end their grief.

Mr O'Brien said the family had avoided the spotlight  but wanted to make a statement on behalf of their son.

"It is the only thing we can do in response to the evil that has occurred," he said. "We don't claim to speak for the other families although we are bound together by this awful thing.

"We and those who died are not anonymous. We cannot do anything to bring them back, but we can say their names and celebrate their lives. And we can tell those responsible what they've done."

Mrs O'Brien said Jack had been taken when he was just about to embark on adulthood. Every morning she sits on the back steps near his bungalow and cries.

"We are powerless in our grief, except for our ability to speak the truth," she said. "We do want the people directly responsible and those who backed them to be accountable."

The O'Briens heard on the kitchen radio that their son's plane had gone down early in the morning and have since avoided the news, putting flowers in front of the television and not turning it on for two months.

They attended the memorial service in Melbourne for the Australian victims on board MH17 and said they were comforted by the fine, strong  and compassionate speeches given by Mr Abbott, the Opposition Leader Bill Shorten and the Governor-General Sir Peter Cosgrove.

As the days passed they received phone calls from Mr Abbott and Premier Mike Baird and were kept up to date with latest developments by officers from the Department of Foreign Affairs and Trade. Their son's body came home to Australia about seven weeks ago.

He was among 298 who lost their lives, including 38 Australian citizens and residents, when the aircraft was presumably shot down by  Russian-backed Ukrainian separatists.

Jack O'Brien was returning from a seven-week holiday in Europe when he boarded the Malaysia Airlines flight in Amsterdam.

He had attended Northmead Primary School and Model Farms High School before graduating from the University of Western Sydney with a degree in business and commerce majoring in sports management. He was working in sales at Fitness First in Carlingford and studying part time to become a personal trainer.

He was returning to Sydney to play for the Winston Hills Soccer Club, a club he had been playing with since the under 8s.

Mrs O'Brien said Jack's death had not only shattered the immediate family – the couple also have a daughter who is attending university – but aunts, uncles, cousins, workmates and teammates.

"The ripple effect just keeps going and will do so for the rest of our lives."