Now John's family is making a desperate plea to the State Parole Authority to keep his killers behind bars.

John's younger sister, Melissa, has spoken out about the horrifying abuse she witnessed as a three-year-old in their effort to prevent Hughes seeing freedom.

"I've just had to stand there and watch my brother get murdered knowing I couldn't do anything," she said.

"They murdered a six-year-old boy for no reason and in the meantime my brothers and I have to suffer."

Last week, after Hughes had served 16 years of a 19-year sentence, the parole authority recommended he be released into the community. All that stands between Hughes and freedom is a public hearing in Parramatta on November 10.

There, John's surviving siblings, his aunt and other family members will have their last chance to make submissions opposing his release.

John's mother, who cannot be identified for legal reasons, applied for parole earlier this year, but was refused.

Hughes and John's mother were originally sentenced to 21 years' jail in 1994 after they pleaded guilty to murder.

However, in separate appeals, they both had their sentences reduced to 19 years.

Their non-parole periods ended two years ago and their sentences are due to expire in August 2012.