In a hearing in the NSW Supreme Court on Thursday, a statement by Greg Simms was read out describing how the loss of his sister had impacted generations.
"We considered you an equal in all respects. We trusted you. You repaid us by committing the ultimate betrayal," Mr Simms wrote.
Thursday's sentencing hearing comes 10 weeks after Dawson, now 74, was found guilty of murdering his wife in January 1982 so he could have an unfettered relationship with one of his high school students, known as JC.
"It was a brazen act of a conniving monster hell bent on one thing, getting what you wanted at any cost," Mr Simms said.
Justice Ian Harrison is hearing submissions from both crown prosecutors and Dawson's legal team about the length of jail time that should be imposed for the murder.
In a five-hour judgment delivered on August 30, the judge outlined why the Dawson was guilty of killing his wife and disposing of her body.
"I am left in no doubt. I am satisfied beyond reasonable doubt that the only rational inference (is that) Lynette Dawson died on or about 8 January 1982 as a result of conscious or voluntary act committed by Christopher Dawson," Justice Harrison said.
Mrs Dawson went missing from the couple's Bayview home in Sydney's northern beaches four decades ago. Her body has never been found despite extensive police searches.
Dawson has consistently denied any involvement in his wife's disappearance, claiming she simply up and left her family home and children without a trace.
Justice Harrison rejected this version of events as "ludicrous".
Two days after the judgment, a lawyer for the ex-Newtown Jets rugby league player told the court that his client had already received death threats while at Silverwater prison due to the high profile nature of the case.
The case shot into the public eye largely as a result of The Teacher's Pet podcast by The Australian's Hedley Thomas which garnered millions of views across the globe.
On the day of the guilty verdict, police confirmed the investigation into Mrs Dawson's murder was not over and urged anyone with information to come forward.
Dawson has already filed an appeal of his conviction.
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