William Mulholland was born in Belfast, Ireland, part of the United Kingdom. His parents Hugh and Ellen Mulholland were Dubliners and they returned to the city a few years after William's birth. His younger brother, Hugh Jr., was born in 1856. At the time of Mulholland's birth, his father was working as a guard for the Royal Mail. In 1862, when William was seven years old, his mother died. Three years later his father remarried. William was educated at O'Connell School by the Christian Brothers in Dublin. After having been beaten by his father for receiving bad marks in school, Mulholland ran off to sea.
