The daughter of Borce Ristevski has reacted angrily to claims her estranged stepbrother was having an affair with her Kiwi mother, Karen.
She has labelled the allegations "completely untrue".
Sarah, a 24-year-old graphic designer, has spoken publicly for the first time since her father was jailed for killing her beloved mother Karen despite vigorously protesting his innocence and playing the grieving widower.
In a 60 Minutes' interview, which aired on Channel 9 on Sunday night, the couple's daughter struggled to answer why she still supports her father.
Ristevski, 55, entered a shock last-minute guilty plea to the manslaughter of 47-year-old New Zealander Karen Ristevski – his wife of 27 years – but has never revealed details of what actually happened. Carrying his deadly secret cost him an extra four years in jail after his jail term was increased in 2019.
• Sarah Ristevski breaks silence on mother Karen's death, support for father
• Sarah and Borce Ristevski are still 'inseparable'
• Daughter of slain Kiwi mum Karen Ristevski on why she still supports her father
• Australian Borce Ristevski jailed for killing Kiwi wife Karen
Presenter Liz Hayes at one point asked Sarah about claims by her stepbrother Anthony Rickard that he had entered into a relationship with her mother.
Rickard is a son of Ristevski from a previous marriage.
An upset Sarah said the allegations were "completely untrue".
"It could never be true," Channel 9 reported her as saying.
"It's completely unforgivable."
But when asked if she had ever confronted Rickard about them, she said she hadn't spoken to him since 2014.
"How did your father react to that allegation?" asked Hayes.
"He was extremely angry. Just the fact that someone could say that about my mum".
Details of her mother's death shocked Australia as did Sarah's decision not to provide a victim impact statement, instead choosing to write a glowing reference for her father describing him as "loving, caring, sympathetic, protective and charismatic".
When questioned about whether she had ever directly asked Borce if he killed her mum, a clearly emotional Sarah replied, "I asked him. I asked if he'd had anything to do with it."
"And your father said what?" Hayes replied.
"He said 'no'," Sarah said.
"Do you still believe him?"
"He's my dad and nothing has changed," Sarah said.
"Even though he's pleaded guilty I find it hard to comprehend that he is guilty. I think if he were in my position he would support me.
"He's my father. I have one parent left … I loved him before, I love him now and I'll love him in 11 years when he's home."
Karen disappeared from the family home in Avondale Heights, northwest of Melbourne, in June 2016. Her body wasn't found until February 20, 2017 in bushland off Loch Rd at Mount Macedon.
For years, Borce Ristevski repeatedly denied having any involvement in her death – and to this day, Australia is none the wiser as to how she was killed.
In December last year, Ristevski was resentenced at the Victorian Court of Appeal. He was initially given nine years' jail but that was increased to 13 years with a minimum of 10 years after an appeal by prosecutors.