Eustace IV, Count of Boulogne Eustace IV, Count of Boulogne Eustace IV (c. 1127–1135 – 17 August 1153), Count of Boulogne, was the eldest son of King Stephen of England and Countess Matilda I of Boulogne. When his father seized the English throne on Henry I's death in 1135, he became heir apparent to the English throne. Upon his mother's death in 1152 he inherited the county of Boulogne and other estates. Eustace was first mentioned in one of his parents' charters dated no later than August 1131. As heir to the English throne in 1137, he did homage for Normandy to Louis VII of
Henry I of England of the senior clergy in England and Normandy. Henry's only legitimate son and heir, William Adelin, drowned in the "White Ship" disaster of 1120, throwing the royal succession into doubt. Henry took a second wife, Adeliza of Louvain, in the hope of having another son, but their marriage was childless. In response to this, Henry declared his daughter, Empress Matilda, his heir and married her to Geoffrey of Anjou. The relationship between Henry and the couple became strained, and fighting broke out along the border with Anjou. Henry died on 1 December 1135 after a week of illness. Despite his