Murderer Vincent O'Dempsey is "beyond redemption" and will likely die in jail for killing Barbara McCulkin and her two daughters 43 years ago.
His accomplice, Garry "Shorty" Dubois, is also expected to spend his final years behind bars if he remains silent about where the family's bodies are buried.
Mrs McCulkin's brother Graham Ogden said finding the remains was an enduring hope of the slain trio's surviving family members.
"It is my fervent wish that some day, the remains of our loved ones will be found so that we can finally lay them to rest," he said in a statement read in court.
"They should be with us still, leading rich and vibrant lives."
But the pair convicted over their deaths continued to proclaim their innocence as they were given life sentences in the Brisbane Supreme Court on Thursday, with Dubois even being led away after an outburst.
"I've never spoken to police, that's the truth," Dubois said.
"You had your chance at trial, now shut up," Justice Peter Applegarth replied.
O'Dempsey, 78, and Dubois, 70, took Mrs McCulkin and sisters Vicki, 13, and Leanne, 11, from their Highgate Hill home on the night of January 16, 1974.
The court heard Mrs McCulkin worked hard to raise her children, with little financial support from her estranged husband Billy, and the girls would have welcomed a ride in O'Dempsey's flashy car, an orange Charger.
The trio was then driven to bushland near Warwick and tied up.
Based on a confession Dubois made to fellow gangster Peter Hall in 1974, it is believed O'Dempsey led the 34-year-old mother away from the children and strangled her.
Dubois' trial in November 2016 heard O'Dempsey raped one of the girls, although he was not tried on that charge, and asked Dubois to rape the other.
"Like a coward, you did what you were told," Justice Applegarth told Dubois.
"It is hard to imagine a worse case of rape.
"The girls must have known their mother had been killed. They must have known, as you did, that they were to be killed."
Both men were convicted at separate trials of the sisters' murders but Justice Applegarth said it was O'Dempsey who had killed them and Dubois did not raise a finger in opposition.
"You murdered a defenceless woman, you are a child killer - you are beyond redemption," he told O'Dempsey.
"Even if you live to be 100, I expect you will die in jail."
O'Dempsey broke his silence before the sentencing, stating to the court he was "completely innocent".
"I have never had the slightest reason to harm the three McCulkins in any way, nor did my co-accused," O'Dempsey said.
But Justice Applegarth found O'Dempsey's protest of innocence "completely unconvincing" and said it confirmed he had a "complete absence of remorse".
"You were the principal offender in each brutal killing," Justice Applegarth said.
Justice Applegarth also told Dubois he could not expect to be granted parole if he remained silent.
"The only issue for Dubois is whether he spends the rest of his life as the coward he was on the night of 16 January, 1974," he said.
