Earl of Brandenburg Ansbert de Brandenburg et hainant, Lord Duke of Mosel - duplicate family

"Earl" is strictly a British title, not used on the Continent. The equivalent would be "Count" (which isn't used in England except as the feminine equivalent, probably because "Earless" sounds stupid).

On the other hand, if he has a higher title, you use that one and put the lesser titles in "Also Known As" or "About".