Jameson Parker, Jr. was born in Baltimore, Maryland, on November 18, 1947. He was the son of Jameson and Sydney Buchanan (née Sullivan) Parker. His father had been general legal counsel for the Parker family steel mill, an investment analyst, and government attorney (working first with the Maryland Public Expenditure Council and later with the United States Naval Reserve). In 1947, he was in private practice, but about to embark on a career as a diplomat with the United States Department of State.