There Joscelin married an English heiress, and through his son, the House of Percy—as the Earls and later the Dukes of Northumberland—became the most powerful family in Northern England.

He was a son of Godfrey I, Count of Louvain by an unnamed mistress [4] Joscelin was granted the manor of Petworth, in Sussex, by his half-sister Adeliza of Louvain, the widow of King Henry I of England.

Though they originally intended Petworth to be their southern home, the Earls of Northumberland were confined to Sussex by Elizabeth I in the late 16th century, when she grew suspicious of Percy allegiance to her rival, Mary, Queen of Scots.

[2] He married Agnes de Percy (d.1203), one of the two daughters and co-heiresses of William de Percy (d.1174/5), 3rd feudal baron of Topcliffe, Yorkshire.

[6] and Alice de Clare, descendant of Richard I of Normandy.