In 1609, the senior line of the Counts of Roeulx became extinct, and the county passed to a cadet branch, represented by Eustache de Croÿ (1608-73), governor of Lille and Douai.
Probably the most illustrious member of the Croÿ-Roeulx branch was Eustache's nephew, Charles Eugène de Croÿ (1651-1702).