David Charles BRUCE-SMYTHE was the son of Captain Reginald Walter Oliver Joseph BRUCE-SMYTHE, MC (formerly BRUCE; 1894 - 12 I 1969) and his wife (married 1933), Gertrude Mary Barbara EYRE (14 XI 1911 - 3 XI 1976), of that landed gentry family, of Lindley Hall. Captain Reginald BRUCE-SMYTHE was the elder son of Archibald Dacres Austin BRUCE (15 V 1869 - 1941) and his wife (married January 1894), Ismay Ursula Annunciata SMYTHE (1867 - 4 I 1951), younger daughter of Sir (John) Walter SMYTHE, 8th Bt (7 XI 1827 - 5 III 1919) and his wife (married 8 II 1864), Louise Marie HERBERT, of that landed gentry family of Clytha Park, near Abergavenny, Monmouthshire.
Captain Reginald BRUCE-SMYTHE succeeded to the Acton Burnell estate on the death of his uncle, Captain Sir Edward Walter Joseph Patrick Herbert SMYTHE, 9th and last Bt (20 III 1869 - 9 III 1942). Captain Bruce-Smythe was a 4 x greats-grandson of Sir John Smythe, 3rd Bt (died 17 IX 1737); he was therefore a first cousin four times removed downwards of Sir John's granddaughter, Mrs Maria Anne FITZHERBERT, formerly WELD, née SMYTHE (26 VII 1756 - 27 III 1837), who, twice widowed, in 1785 contracted a marriage with the then Prince of Wales (later KING GEORGE IV), which was in contravention of the Royal Marriages Act 1772 and, as such, not valid under English law.
Gertrude Mary Barbara EYRE was the daughter of Stanislaus Thomas EYRE (17 VII 1867 - 1951) and his wife and first cousin twice removed downwards (married 29 XI 1900), Gertrude Mary Tessa NORRIS (19 X 1878 - 1973). Stanislaus was the son of William Francis EYRE (14 VII 1793 -1885) and his second wife (married 7 I 1864), Ellen Josephine WITHAM (c.1834 - 1889); Gertrude was the daughter of Anthony NORRIS (c.1818 - ?) and his wife (married 12 X 1868, as her first husband), Julia Mary EYRE (c.1850 - ?), who was herself a daughter of Vincent Anthony EYRE (8 VIII 1809 - 22 III 1887) and his first wife (married 6 IV 1842), Anne HUDDLESTON (c.1818 - 19 IV 1881); Vincent Anthony EYRE was the eldest son of Vincent Henry EYRE (20 I 1775 - 5 VI 1851) and his wife (married 1808), Mary WRIGHT (died 19 XII 1854). Vincent Henry EYRE was the eldest brother of the aforementioned William Francis EYRE, whose son married his great-granddaughter.
Archibald Dacres Austin BRUCE was the son of the Rev William BRUCE, MA (6 IX 1816 - 28 III 1894; a younger brother of the 1st Baron Aberdare) and his second wife (married 14 VII 1868), Margaret Harriet OLIVIER (c.1829 - 16 XII 1923), daughter of Lt Col Henry Stephen OLIVIER (14 VIII 1796 - 21 II 1864), who was the grandfather of Sydney Haldane OLIVIER, 1st and last Baron Olivier, KCMG, CB, PC (16 IV 1859 - 15 II 1943) and the great-grandfather of the latter's nephew, the Life Peer Laurence Kerr OLIVIER, Baron Olivier, OM (22 V 1907 - 11 VII 1989).