• Born: Boulogne-sur-Mer, Pas-de-Calais, France
• Married: 1102
• Died: 1125 or after

  Research Notes:

His parentage is specified in his donation to Saint-Bertin dated 1122, for the souls of "Eustacii comitis patris mei et Yde matris mee comitisse". He is not named as one of her sons by "Ida comitisse Boloniensis" in the latter's charter for the soul of her husband. William of Tyre records him as brother of Godefroi and Baudouin, naming him last of the three. It is not known whether this indicates that he was the youngest of the three brothers, or was simply a reflection of his less significant role in affairs in Palestine. His inheritance of the paternal possessions and titles suggests that he was the oldest brother, at any rate older than his brother Baudouin.

He succeeded as Comte de Boulogne, Comte de Lens. This would normally be an indication of his seniority in the family. However, given the superior position of his brother Godefroi as Duke of Lower Lotharingia, it may have been decided that the less important paternal inheritance would pass to a younger son. He was a member of the company of Robert II Count of Flanders on the First Crusade, joining his brothers after arriving in Constantinople in 1097. Albert of Aix records the arrival in Constantinople of "Robertus Normannorum comes, Stephanus Blesensis, Eustachius frater prædicti Ducis", dated to early 1097 from the context. In Palestine in 1099, he returned to Boulogne soon after. "Eustacius Bolonie comes" confirmed the possessions of the abbey of Samer by charter dated Jul 1112, subscribed by "Cononis de Fieules, Eustacii et Rogerii filiorum eius…". Albert of Aix records that Baudouin appointed "fratri Eustachio" as his successor on his deathbed if he would come to Jerusalem, or if he failed to come "Baldewinus de Burg". A legation left Jerusalem for Boulogne in Apr 1118 to invite him to succeed. Eustache left Boulogne for Jerusalem, but when he reached Apulia he received news that Baudouin du Bourg had been chosen as king. He refused to press his claim further, and retired to the Cluniac monastery at Rumilly in [1125]. "Eustachius olim comes Boloniensis nunc autem…monachus Cluniacensis" donated property to Cluny by charter dated 1125 which names "Maria uxore mea…[et] Mathildi filia mea", and is subscribed by "Stephani comitis Bolonie, Matildis comitisse. ¹