 Born in Hambledon, Surrey, England, on 26 May 1917, Stocker was the son of Eustace Dupuis Henchman Stocker and Ruth Mary Richmond Stocker (née Hursthouse).Eustace Stocker was a military officer who won the Military Cross in World War I, and was appointed an Officer and then Commander of the Order of the British Empire during World War II.Ruth Stocker was the daughter of Richmond Hursthouse, a Member of Parliament and cabinet minister in New Zealand.