Grace was born at Stowe, Kilkhampton, Cornwall,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 89. the daughter of John Granville, 1st Earl of Bath, and his wife Jane Wyche. Some sources give her date of birth as 1654, which would have made her thirteen years older than her husband. However, their marriage took place in 1675, when she is said to have been "a mere child".
