Le Fleming married Ethel Hall, the daughter of a Lieutenant-Colonel in the Indian Army, in 1891. Both of his sons served during the Great War, the eldest, John Neville, as a Lieutenant with 1/1 Kent Cyclists in India and, in 1919, in the Third Anglo-Afghan War. The youngest, Roger Eustace, attended Sandhurst and served in France in 1915 with the 1st Battalion East Surrey Regiment, fighting at Hill 60 and Second Ypres, before transferring to 102nd Prince of Wales's Own Grenadiers, an Indian Army unit, with whom he fought in Mesopotamia and Palestine and then, in 1919–1920, Somaliland. He was wounded twice, Mentioned in Dispatches and awarded the Military Cross. After the war Roger remained in the Army, serving throughout World War II and eventually rising to the rank of Major-General.