 Jack was the only child of Thomas Kilfoyle, a farmer from Ireland, and his native-born wife Catherine.In 1882 and 1883, Tom had led an overlanding party with his relatives, the Duracks and the Byrnes, and established Rosewood station, which extended from the eastern Kimberley region of Western Australia into the present Northern Territory.Jack was educated in the early 1900s at Christian Brothers' College in Perth.