Her father, José Fernández, a Spaniard, and her Cuban mother, Sylvia Fernández, settled in the Dominican Republic after marrying. The younger of two sisters, María José, who would later use the professional name of Mary Joe, was born on August 19, 1971. While still an infant, her parents moved to Florida, where she first discovered tennis. José, a recreational tennis player, would often take both his daughters to the tennis court. While he played tennis with the older sibling Sylvia, three-year-old Mary Joe would stay out of trouble by hitting tennis balls against the wall with her own tennis racquet.