John William Dunne was born on 2 December 1875 in Curragh Camp, a British Army establishment in County Kildare, Ireland. He was the oldest son of Irishman Sir John Hart Dunne KCB (1835–1924) and his English wife Julia Elizabeth Dunne (née Chapman).[2] Despite being born in Ireland of an Irish father, he had an English mother and was born in Ireland only because his father was Lieutenant-Colonel of the British 99th (Lanarkshire) Regiment, who happened to be stationed there at the time.[3]