Graham Mark Morrison, 55, was tired and near the end of an 11-hour trip from Brisbane to Dubbo when his B-double crashed into the Queensland family-of-five on May 6, 2017.

The force of the crash tore off a rear passenger door and caused the family car to spin, ejecting the two boys and killing them instantly.

Taite, 12, and Kobi, 9, Van Der Heyden died.

NSW District Court Judge Warwick Hunt set a minimum term of 21 months after finding exceptional circumstances including Morrison's "pungent remorse" and his wife's terminal cancer.

The south-bound truck's dashcam showed the B-double moved into the northbound lane of the Newell Highway 36 times in the 25 minutes before the crash.

"(Morrison) was on notice for some time that he was tired ... there were opportunities for him to stop and his determination to continue means his moral culpability is more than low," Judge Hunt said.

"I have no doubt he will punish himself for the rest of his life for those decisions."

The family was returning to Gladstone from Warrnambool in Victoria when the crash occurred about 3.30am.

Their father saw the truck emerging from scrubland on the passenger side and swerved right in an attempt to avoid it.

As the only person to escape the crash with minor injuries, he searched the dark road by torchlight and found the bodies of his boys.

Morrison was trapped in his truck, which ended up in marshland.

The crash would continue to cause heartache for the crash survivors including the boys' younger sister, Judge Hunt said.

Morrison had an enviable record for a professional driver until that point and couldn't explain why he didn't pull over to rest, the judge said.

During tearful evidence on September 6, Morrison said the crash had left him so traumatised he couldn't drive or play with his children without thinking of the boys.

"I'm broken, a bastard ... I've done the unspeakable," he told the court.

"It has changed me beyond belief. Yes, I am despicable."

He had also been forced into severe financial difficulty in order to support his wife and cover his own his medical and legal bills.

Judge Hunt said he had a profound impression Morrison would never absolve himself from the costs of his offending driving.

"I've never heard more pungent remorse."

He noted Morrison would spend his time in jail wondering whether his wife would be alive when he was released.

Morrison will be eligible for parole in June 17, 2021.

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