He was the son and heir of Sir Thomas Grenville by his second wife Elizabeth Gorges, daughter of Sir Theobald Gorges, K.B., lord of Wraxall, Somerset, and Braunton Gorges, co.
Sir Thomas was himself ancestor to famous descendants, most notably his great-great-grandson Sir Richard Grenville (1542-1591), the valiant captain of "The Revenge" and of Sir Bevil Grenville (1596-1643), MP and famous Civil War commander, father of John Grenville, 1st Earl of Bath (1628-1701).