It looks like Kathy Donnelly, the biological mother of the "love child" was mistaken about the real biological father for all of these years.
The man publicly embraced by Tony Abbott as his long-lost love child is the child of another man.
As my grandmother always used to say about women such as Kathy Donnelly who swear they know the father, "If you pitched your ass up against a buzzsaw, could you swear which tooth hit you?"
(h/t Tim Blair)
You've been told and NOW YOU KNOW.