The House of Percy is an English noble family. They were among the most powerful noble families in Northern England for much of the Middle Ages. The noble family is known for its long rivalry with the House of Neville, another family powerful in northern England during the 15th century. The Percy-Neville feud provoked the War of the Roses, at the time known as the Civil Wars, in England. The House of Percy descends from William de Percy (d. 1096), a Frenchman who crossed over to England after William the Conqueror in early December 1067. William was created 1st feudal baron of Topcliffe in Yorkshire. He was rebuilding York Castle in 1070. The Percy surname derives from the manor of Percy-en-Auge in Normandy, the home of the Percy family at the time of the Norman Conquest. Family members have held the titles of Earl of Northumberland or Duke of Northumberland to this day, in addition to Baron Percy and others. The Percy surname twice died out in the male line only to be re-adopted later by the husband or son of a Percy heiress. In the 12th century, the original Percy line was represented by Agnes de Percy, whose son by her husband Joscelin of Louvain adopted the surname. Again in the 18th century, the heiress Elizabeth Seymour married Sir Hugh Smithson, who adopted the surname Percy and was created Duke of Northumberland. Earls of Northumberland Dukes of Northumberland Recurring names Recurring names in the Percy genealogy include: Henry (first borne by the 7th feudal baron of Topcliffe and his 10 immediate successors, including the 1st Earl and Harry Hotspur) Hugh (first borne by the 1st Duke) Joscelin/Josceline (first borne by Joscelin of Louvain) Algernon (first borne by the 1st Baron as a nickname: Aux Gernons or "with moustaches"). Prominent members Prominent members of the family include: (d. 1096), 1st feudal baron of Topcliffe, Yorkshire, nicknamed "Aux Gernons" ("with moustaches"), a Norman who emigrated to England at the time of the Conquest Alan de Percy, 2nd feudal baron of Topcliffe (d. circa 1130–5) William II de Percy, 3rd feudal baron of Topcliffe (d. 1174–5), who left two daughters Maud and Agnes as co-heiresses. Agnes de Percy (1134-1205), married Joscelin of Louvain (d.1180). He was a son of Godfrey I, Count of Louvain of the House of Louvain, ancestor of the Dukes of Brabant , House of Hesse, and so the