Hadfield Smith, of Gisborne, was speaking at the inquest into the death of his son, Stewart Hetaraka Smith (20), and Lavenia Setefano (19), who died in a van crash on their way to work two years ago.
Stewart Smith was a shearer and Ms Setefano was a woolhandler.
"We can't bring them back for you but we can put in place measures to prevent this happening again," Otago-Southland coroner David Crerar told the families.
The inquest could look into the circumstances of the deaths and focus on giving recommendations to the public, the shearing industry and the Department of Labour, to avoid deaths in similar circumstances in the future, he said.
Mr Smith said it had been a difficult two years for the families.
"We've been struggling with it and we always will."
"When you wanted workers, I sent my son, and now we're left looking at a headstone," he told his son's employer, Dion Morrell, during the inquest.
Safety measures had been improved since the accident, and he commended Mr Morrell for that, "but it's too late for us".
Mr Smith said he hoped his son had not died in vain.
The father of Ms Setefano, Joe Setefano, of Gore, said he shared the Smith family's pain.
"We can never replace our children, but we hope we can stop this happening again in the future."
After the inquest, Mr Setefano said his daughter, whom they called Nia, was the eldest of his three daughters.
Two were still working in the shearing industry.
"It brings it home every day, when the girls go to work, " he said.
Nia had lots of plans for the future and wanted to join the navy and to travel.
Mr Smith said Stewart was a three-time finalist in the country's most prestigious shearing competition, the Golden Shears. He had competed in the junior section in 2006, the intermediate in 2007 and the senior in 2008.
His son had also owned a house, paying it off by the time he was 20.
"Our young people, they were just starting to blossom, like flowers," he said.
Mr Crerar has reserved his decision but said Mr Smith and Ms Setefano's failure to wear seat belts the day of the crash was a significant contributing factor in their deaths.
