On the eve of his sentencing, the elderly couple said they just
wanted a proper burial for their daughter.
The dead woman's three children have even chosen a headstone so she can finally be laid to rest.
But Thomas Keith Halliday, 46, refuses to give up his macabre secret.
A Supreme Court jury last month found the Mildura delivery driver guilty of murdering Shelley Joy Stephenson.
His plea hearing begins in Mildura on Wednesday and he is expected to be sentenced on Friday.
Police accused him of killing Ms Stephenson by strangling her or a karate chop to the throat.
They allege he jammed her body into a disused hot water service cylinder which he then packed with gravel and dumped in the Murray River.
Asked in his record of interview with police if he killed Ms Stephenson, Halliday replied: "I can't say I did . . . and I can't say I didn't."
Her family now lives in hope Halliday will end their torment and reveal where he hid her body.
"Tell the kids where their mother is," mother Lynette Stephenson pleaded.
"Tell us where our youngest girl is. Tell us so we can give her the decent burial she deserves. Everybody deserves to be buried properly."
Police have dragged the river for her remains without success. The Stephenson family have also searched the banks of the Murray.
"The river's a big place. It's dropped a fair bit, but you never know . . ." Shelley's father John said.
Ms Stephenson was last seen in Mildura early on March 2, 2006.
Halliday reported her missing five days later at his local police station in Merbein West, 15km west of Mildura.
Ten weeks later detectives from the homicide squad's missing person unit were called in to investigate her suspicious disappearance.
At the time Ms Stephenson, 34, was estranged from Halliday. She had fled his home with her two young daughters, Sarah, 11, and 10-year-old Christie, to live in Mildura.
Her son Michael, 9, had been living with her parents for the previous 12 months.
It was her fourth attempt to leave Halliday.
Lynette Stephenson said Halliday controlled her daughter and the children through abuse and violence.
"I honestly believe they won't find her. He has to tell them," she said.
"She's got a little girl who wants to find mum and go to the coffin shop and buy her a coffin. She wants a heart-shaped head stone for her mum. She's picked one out.
"It's been too hard to bear, so we put a plaque on my parents' grave in Red Cliffs and we go there on Shelley's birthday and we let balloons go. We do it for the kids, it makes them feel good.
"Sarah has bought her an angel, because Shelley's up there with the angels."
Lynette and John Stephenson, 64, now care for the three children.
Mr Stephenson said his grandson had endured psychological torment and physical violence from Halliday.
Mrs Stephenson said her daughter knew Halliday for eight years before their relationship started.
He was a volunteer bus driver for the support group "Homemakers" that Shelley attended as a single mother.
"It's just not fair. She didn't deserve any of it," her mother said.
"All she needed was a good man. She was just used and abused."