The Grenville family descend from Rollo, a noble chieftain of Norway, who being driven thence by the King of Denmark, attempted with his followers a descent on England, but experienced a repulse from Alfred. In the year 870, he made an irruption into Normandym which conquest he completed in 912. He was afterwards invested with the title of duke of Normandy, and married Gilbette, daughter of Charles the Semple, king of France, by whom he had two sons, From William, the eldest, descended William the Conqueror, and the succeeding kings of England; and from Robert, the second son, created earl of Corbeil, descended Hamon Dentatus, the sixth earl of Corbeil, who had two sons, by Elizabeth D'Avoye, his near kinswoman, widow to Hugh the Great, and sister to the emperor Otho. The eldest was called after his own name, Robert Fitz Hamon; the second son, Richard, (as is still the custom in those countries) after the name of one of his lordships, Granville which surname of Granville, or by corruption Grenville, Greynville, Grenfel, Greenfield, Graynefield, and Granvilia, has remained to his posterity ever since.

The two brothers, Robert Fitz Hamon, and Richard de Granville, accompanied William the Conqueror in his expedition into England, and were present with him at the great battle near Hastings in Sussex, where king Harold was slain. For their signal services, the Conqueror bestowed on them large gifts and honoursm particularly to Richard de Granville, the castle and lordship of Bideford, Devon, with other lands, lordships, and possessions, in Cornwall, Devon, Somerset, Gloucestershire and Buckinghamshire.

After the death of the Conqueror, the said Robert Fitz Hamon, choosing twelve knights for his companions, of whom his brother Richard was one, entered Wales with an army, slew Rheese, their prince, in a pitched battle, and making an entire conquest of Glamorganshire, obliged the rest of the country to pay tribute to the king of England. To reward these and other great services, and being his near kinsman, William Rufus made the said Fitz Hamon, a free prince in all his conquered lands, holding them in vasalage of the king, as his chief lord, which the said Fitz Hamon divided between himself and his twelve knight companions, William Rufus dying, he was, by Henry 1, sent as a general of his army against France, where he received a wound from a pike on his temples, of which he died; and leaving a daughter Mabel, the wife of Robert de Council, natural son to Henry 1, he in her right, enjoyed great part of his lands in England.

Richard de Granville, as the heir male, inherited by the Norman laws, all the estate and honour of his family in Normandy, and thereby became earl of Corbeil, baron of Thorigny and Granville. He had also for his share of the lands taken from the Welsh, the old castle of Neath, in Glamorganshire, and Juia Regalia, in that territory: there he founded an abbey for religious monks, and endowed it with all the lands he held in Wales. Leland says, that the town of Neath (so called by the Welsh) had the name of Granville. In his old age, according to the devotion of those times, he took on him the sign of the cross, and setting forward for Jerusalem, died on his journey, thither, leaving issue by his wife Constance, only daughter of Walter Giffard, earl of Buckinghamshire and Longueville.

Richard, his son and heir, who held in the reign of Henry 11, the lordship of Bideford, Devon, by half a knight's fee of the honour of Gloucester. In the second of king John, being stiled lord of Bideford and Kilkhampton, he paid forty marks and a palfrey to have an assize of the advowson of these two churches, against the abbot of Tewkesbury. In the twelth of the same reign, he held three knights' fees and a half in the counties of Cornwall and Devon and died in the first of Henry 111. He married Adeline, widow of Hugh Montfort, eldest daughter of Robert de Bellemont, earl of Mellant in France and the first earl of Leicester in England, after the conquest, by Elizabeth, daughter of Hugh, the great earl of Vermandois, son to the king Henry of France: to him succeeded Richard de Granville, his son and heir, under age at his father's death. He married Jane, daughter to William Trevint. Richard his eldest son married Catherine, daughter of Josceline, of Mount Tregiminion, and died without issue. Bartholomew de Granville, his brother became his heir. By his wife Anne, daughter of Sir Vyell Vivian, of Trevideren, in Cornwall, he left Henry his son and heir, who enjoyed the manor of Kilkhampton and Winkleigh, with the honour and manor of Bideford etc. He left issue by his wife Anne, daughter and heiress to Wortham.

Sir Theobald, his son and heir, under age, who became ward to Sir John Carew. He married Joice, daughter of Sir Thomas Beaumont, knt., by whom he had Theobald, his son and heir, who married Margaret, daughter of Hugh Courtenay, earl of Devon, and had two sons; John, who married Margaret, daughter and heiress of Sir John Burghursh, (her sister Maud was married to Thomas Chaucer, the writer). He lived at Stowe and was knight of the shire, for the county of Devon, in several parliaments, but died without issue, leaving William his brother and heir, to succeed him, who died about the twenty-ninth of Henry V1, leaving issue by Phillipa, his second wife, sister of William Lord Bonville, Thomas his son and heir, (ancestor of Prince William) and two daughters, Ellen who married William Yeo of Heanton Satchville, (ancestor of most of the Yeo descendants), and Margaret who married John Thorne of Thorne in Cornwall. Thomas was knighted in the seventeenth year of Henry V11 reign and married Elizabeth Gorges, sister to Theobald Gorges, knt.