The grieving parents of two young boys tragically killed in a crash while heading off on holiday are desperately pleading with motorists to take care as their loss sinks in deeper and hurts more every passing day.

Hamilton couple Dr Mohadeseh Sharifi and father Siamak Mosaferi were travelling to Wellington on Good Friday with their two young boys in the back seat when their car crashed with three other vehicles, including two truck-and-trailer units, on the Desert Rd near Waiouru.

Their eldest son Arteen, 4, died at the scene and his 10-week-old baby brother Radeen died from his injuries two days later at Starship Hospital.

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Eight months on, the boys' devastated parents are now urging motorists to pay attention to the roads as they head off for summer holidays.

They want people to slow down, increase their following distance and pay more attention - actions they believe would have saved their sons' lives.

"After what happened to us this year, we have developed a completely different view on cars, driving habits and roads," the boys' mother said through tears.

"When you are behind a wheel in a car you have the ability to completely ruin people's lives for a whole lifetime with the smallest inattention or mistake ...

"No one, no parent deserves to go through what we have and will be going through the rest of our lives."

She also urged people to be aware of the baby on board signs on a car because they weren't for decoration.

"Baby on board signs are to alert all drivers around that there is a little life on board, which is a lot more fragile and vulnerable.

"When you are driving behind a car with a baby on board sign, bear in mind that your slightest inattention, higher speed, shorter following distance and any other mistake can so easily take away the life of that precious baby or kid on board and as a result of that completely destroy every single person in that car or that family."

Sharifi said losing their two young children was something the couple would never move on from.

Arteen Mosaferi, 4, and his baby brother Radeen, 10 weeks old, were tragically killed in a road crash on the Desert Rd near Waiouru on Good Friday. Photo / Supplied
Arteen Mosaferi, 4, and his baby brother Radeen, 10 weeks old, were tragically killed in a road crash on the Desert Rd near Waiouru on Good Friday. Photo / Supplied

"You can move on from a death of a parent, brothers and sisters - you can move on. But this you just can't. It's always going to be there.

"Everyone has told us time will heal - but it's not. It's just making it sink in deeper and it's making it felt stronger."

Last Christmas the family had a large tree in the corner of their living room and there would have been presents stacked under for Arteen. Young Radeen hadn't even been born yet.

This year, the family home is void of any sign of Christmas.

"This year I just want to run away somewhere - where there's no sign of Christmas. That's all I want to do," Sharifi said.

"I'm not in a holiday mode, I'm not in a trip mood - nothing. The only reason I'm going (away) is just to be away from home and not feel that gap."

Since the crash, their parents had a completely different perspective on driving and their senses were heightened.

Mosaferi said he was often scared by other motorists' behaviour during his 10km drive from home to his office near Hamilton's CBD.

Since his boys' death, he had installed dashcams in the front and back of his car and in the past three months since he had started driving again, he had witnessed eight near-misses.

People were speeding, tailgating and swerving over the road and he believed there needed to be more accountability. He had reported the information to the police website.

His wife was still extremely nervous about even travelling in a car, and avoided it when she could.

"I haven't been able to drive since. I go in a car, but I am very anxious about everything."

Truck driver John Barber has been charged over the crash. His trial has been adjourned until February at Taupo District Court.