Craig Folbigg, the former husband of Kathleen Folbigg, has died months after she was acquitted of killing their four children after decades in prison.
Mr Folbigg had suffered a heart attack and was also dealing with cancer before his death earlier this week, media reports on Tuesday said.
In a statement released through lawyer Rhanee Rego, Ms Folbigg extended her condolences.
"There were only two people on this earth who knew what it felt like to lose Caleb, Patrick, Sarah and Laura."
"My condolences go to the loved ones Craig leaves behind," she said.
Ms Folbigg was acquitted in the NSW Court of Criminal Appeal over the children's deaths in December after multiple inquiries, the latest of which heard there was reasonable doubt about her guilt after previously undiscovered genetic variants were identified in the children.
Mr Folbigg testified against her in the 2003 trial that led to her spending two decades in prison.
