She was the only child and sole heiress of Thomas Horner (1688-1741) (later Strangways-Horner), MP, of Mells Manor, Mells, Somerset. Her mother was the heiress Susannah Strangways,Mosley, Charles, editor. Burke's Peerage, Baronetage & Knightage, 107th edition, 3 volumes. Wilmington, Delaware, U.S.A.: Burke's Peerage (Genealogical Books) Ltd, 2003. Page 2027. one of the two daughters of Thomas Strangways (1643-1713) of Melbury House in Dorset, a major landowner. The other daughter, Elizabeth Strangways (died 1729), married James Hamilton, 5th Duke of Hamilton, as his second wife, G.E. Cokayne; with Vicary Gibbs, H.A. Doubleday, Geoffrey H. White, Duncan Warrand and Lord Howard de Walden, editors, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant, new ed., 13 volumes in 14 (1910-1959; reprint in 6 volumes, Gloucester, U.K.: Alan Sutton Publishing, 2000), volume VI, page 269. but died childless. Susanna Strangways was the co-heiress of her childless brother Thomas Strangways (died 1726) and, after the death of her sister the Duchess of Hamilton in 1729, sole heiress.
