Sources

1) Source: Chronica Magistri Rogeri de Houdene "In the same year [1196] died William, earl of Salisbury, son of earl Patrick, whose daughter and heiress Richard, king of England, gave to wife, together with the earldom of Salisbury, to William, his bastard brother." (Data from direct source)
2) Source: Court of Wards and Liveries: Deeds and Evidences "Letters patent by which Ela [Longespée], countess of Salisbury grants in her widowhood and liege power, for her soul and that of William Longespée (Lungespeie), her husband, their ancestors, and of William Longespée (Lungespeie), her son, and of all of her other children and heirs, to St Mary and St Bernard and the nuns at Lacock". Date: 1230. External Link
https://discovery.nationalarchives.gov.uk/details/r/C4453660. Reference: WARD 2/28/94E/24 (Data from direct source)