Josef F. may have fathered at least six children with his daughter. The daughter and three of her children apparently lived in hidden rooms in the cellar of his house. Elisabeth, apparently told police that her father drugged, handcuffed and dragged her into a basement back in 1984. The cellar room was accessible only through a hidden door with an electronic code. She said she was a constant victim of sexual abuse and incest.
According to Berthold Kepplinger, "It is astonishing how easy it worked, that the children came together and also it was astonishing how easy it happened that the grandmother and the mother came together." (Elisabeth and two of her children joined with three of her other children and her mother.) Elisabeth's eldest child, 19-year-old Kerstin Fritzl, remains in hospital.