Mr Mason-Hornby was the younger, but only surviving, son of Capt Paul Randle Feilden MASON (19 XI 1893 - 24 V 1944) and his wife (married 14 IV 1917), Joyce Madeline WIGAN (22 I 1898 - ), a granddaughter of Sir Frederick WIGAN, 1st Bt (4 X 1827 - 2 III 1907). Capt Paul Mason was himself the son of Col Henry Paul MASON (25 I 1855 - 11 IX 1924) and his wife (married 28 VIII 1890), Helen Arbuthnot FEILDEN (17 III 1859 - 13 IX 1947), of that landed gentry (LG) family.
Helen Feilden was the elder daughter of the Rev Henry Arbuthnot FEILDEN (7 IX 1828 - 29 IX 1909) and his wife (married 18 VIII 1857), Ellinor Georgina Katherine HORNBY (13 IV 1834 - 17 XII 1910), third daughter of Edmund George HORNBY (16 XI 1799 - 27 II 1863), head of that LG family, of Dalton Hall, Westmorland, MP (Whig) for Warrington, 1832-35, and his wife (married 30 I 1827), Sarah YATES (21 V 1804 - 17 VIII 1886).
Mrs Sarah Hornby, née Yates, was a first cousin of Sir Robert PEEL, 2nd Bt (5 II 1788 - 2 VII 1850), Prime Minister 1834-35 and 1841-46, her father having been a brother of his mother. Her husband, Edmund George Hornby, was a first cousin (twice over) of the 14th Earl of Derby, Prime Minister February-December 1852, 1858-59 and 1866-68, his father having been the eldest brother of Lord Derby's mother, and his mother having been a sister of Lord Derby's father, the 13th Earl.
Edmund George Hornby's successor as head of the family was his only son, Maj Edward Geoffrey Stanley HORNBY (2 I 1839 - 13 I 1923), who died unmarried, and was succeeded at Dalton Hall by his nephew (the only son of his fourth sister), Charles Windham Leycester PENRHYN (5 XI 1873 - 21 IX 1966), of that LG family of East Sheen (which, per Burke's Family Index (BFI), last appeared in Burke's LG in the 1914 edition), who changed his surname to PENRHYN-HORNBY (per BFI, Penrhyn-Hornby (formerly Hornby) of Dalton Hall last appeared in Burke's LG in the 1952 edition). After Mr Penrhyn-Hornby also died unmarried, he was succeeded at Dalton Hall by Anthony Mason-Hornby, his first cousin twice removed downwards.
Anthony Mason-Hornby's wife, Cecily Barbara CARTER (born 1932) was the second daughter of Lt-Col Henry Gordon CARTER MC (1893 - 12 VI 1966) and his wife (married 1924), Cecily Mary Cunningham TRONSON (25 I 1900 - 2 VII 1972).
Cecily Tronson was the second daughter of Henry St George Tucker TRONSON (31 VII 1865 - 21 V 1947) and his first wife (married c.1896), Annie Mabel Faith CUNNINGHAM (1871? - 1902?). Mr Tronson was himself the son of Maj-Gen Robert Nixon TRONSON (1819 - 9 XI 1882) and his wife (married 1861), Maria Jane Durrell COOKE (1842 - 21 XI 1909), a 3 x greats-granddaughter of Sir George COOKE, 3rd Bt, of Wheatley (16 V 1662 - 5 X 1732).
