He was discovered hiding 30 miles away from his hometown at a relative's house in Loreto, Santiago del Estero, northern Argentina.
After undergoing the DNA test, Bulacio was charged with sex crimes and will now stand trial.
According to local reports, the victim was abandoned by her mother, who was allegedly physically abused by Bulacio.
Six of the eight children are living at the boarding school of Eva Peron in Santiago del Estero, local media reported.
There is no further information about the mother, whose name has not been made public.
The case, which has been adjourned until next week, continues.