The Bouwens family is of Dutch origin. The parents of Derek BOUWENS were Bethell Godefroy BOUWENS (9 II 1884 - 24 X 1942) and his wife (married 20 VII 1912, as her first husband), the Hon Margaret Henrietta ("Peggy") DE GREY (15 XI 1889 - 13 VII 1978), daughter of the 7th Baron Walsingham. Bethell Bouwens' sister, Hyacinth Lambart BOUWENS (31 I 1890 - 6 II 1968), was married on 29 April 1919 to his wife's brother, George DE GREY, 8th Baron Walsingham, DSO, OBE (9 V 1884 - 29 XI 1965).
Bethell Godefroy BOUWENS was the son of Lt Col Lambart Henry BOUWENS (16 II 1843 - 20 IX 1902) and his wife (married 23 XI 1882), Charlotte BETHELL (1845 - 19 I 1927). Lt Col Bouwens was himself the son of the Rev Theodore BOUWENS (c.1798/9 - 18 II 1869) and his wife (married 3 VIII 1841), Lady Julia LAMBART (20 II 1821 - 13 II 1897), sister of the 8th Earl of Cavan. Charlotte Bethell's parents were William Froggatt BETHELL (1809 - 7 III 1879), of that landed gentry family, of Rise Park, near Hull, and his wife (married 25 III 1841), Elizabeth BECKETT (1821 - 1870), daughter of Sir Edmund BECKETT, 4th Bt, and sister of the 1st Baron Grimthorpe.