He was s of Beauchamp SEYMOUR 1878-1965 (2xgt gs of 1st Marquess of HERTFORD 1718-94) and Eva Douglas 1897-1949 d of Rev Herbert BROWN of St Lawrence, Southminster, Essex. He m 1st 1958 Alexandra M d of Douglas MACLEOD of The Mill House, Stratton, Dorset, and had 2 sons. He m 2nd 1971 Lavinia Margaret 1947-[10 June]2023 d of Sir William LAWRENCE 4th Bt 1913-86 and Pamela Mary 1920-2012 d of James Edgar GORDON 1886-1976 of Beechbank, Bromborough, Wirral, Cheshire by his 1914 m reg Q3 Cheshire to Dorothy ARKLE 1889-1978, and had a further son (Harry William 1974-2011) and a dau.