Grand Duke

A feudal title that is higher than a Duke, but largely the same responsibilities and power. Grand Dukes command a territory called a Grand Duchy.   The difference between a Duke and an Grand Duke are almost entirely social, as the Grand Duchies are only created to elevate a duke after special service or renegotiations of vassalage.
Type
Nobility, Hereditary
Form of Address
Your Highness
Reports directly to