William Charles Wentworth was born on 13 August 1790 to D'Arcy Wentworth and Catherine Crowley. D'Arcy was the impecunious distant offspring of the aristocratic Wentworth family. D'Arcy was born in Ireland in 1762, but had left to train as a surgeon in London. To maintain his lifestyle he apparently became a highwayman, but soon found himself in trouble with the law. After being acquitted four times of highway robbery, to avoid a further prosecution, D'Arcy took the position of assistant surgeon to the new colony of New South Wales. He boarded the "Neptune" sometime in December 1789. On board the ship was a seventeen-year-old girl from Ireland, who was being transported to Sydney following a conviction for stealing some clothing. On board ship, D'Arcy Wentworth and Catherine Crowley became lovers.