On his death the county of Boulogne came to his daughter, Matilda, and her husband Stephen, count of Blois, afterwards king of England, and in 1150 it was given to their son, Eustace IV.
EustaceIII, was a count of Boulogne, successor to his father Count Eustace II of Boulogne.
Eustace and Mary had one daughter, Matilda of Boulogne.
Eustace was at first uninterested, but was convinced to accept it; he travelled all the way to Apulia before learning that a distant relative, Baldwin of Bourcq, had been crowned in the meantime.
Eustace died in 1093, and was succeeded by his son, EUSTACEIII., who went on crusade in 1096, and died about 1125.
Eustace was knighted in 1147, at which date he was probably from sixteen to eighteen years of age; and in 1151 he joined Louis in an abortive raid upon Normandy, which had accepted the title of the empress Matilda, and was now defended by her husband, Geoffrey of Anjou.
The death of Eustace, which occurred during the next year, was hailed with general satisfaction as opening the possibility of a peaceful settlement between Stephen and his rival, the young Henry of Anjou.