Hudson was born Roy Harold Scherer Jr. on November 17, 1925, in Winnetka, Illinois, the only child of Katherine (née Wood), a homemaker and later telephone operator, and Roy Harold Scherer Sr., an auto mechanic. His father was of German and Swiss descent, while his mother had English and Irish ancestry. He was raised as a Roman Catholic. During the Great Depression, Hudson's father lost his job and abandoned the family. Hudson's parents divorced when he was four years old; a few years later, in 1932, his mother married Wallace Fitzgerald, a former Marine Corps officer whom young Roy despised. Fitzgerald adopted his stepson without his consent, and his legal name then became Roy Fitzgerald. The marriage eventually ended in a bitter divorce and produced no children.