Arnulf I, Count of Flanders
At the death of their father in 918 Arnulf became Count of Flanders. His brother Adelolf succeeded to the County of Boulogne. When Adeloft died in 933 Arnulf took control of Boulogne and Ternois. His nephews were still young so it was probably as their guardian. Later he gave the countship of Boulogne to his nephew, Arnulf II.