In the Early Middle Ages, there were, in each province, a number of feudal lords who often were just as powerful, and sometimes more so, than the rulers themselves.
In the middle of the fourteenth century, quarrels between the feudal lords reduced many families and castles to ruins, contributing to the Dukes of Burgundys' acquisition by conquest or inheritance of many of the provinces forming the Kingdom of the Netherlands.
In 1581, representatives of the Seven Provinces abjured Philip II of Spain, heir of the Dukes of Burgundy.
This left a great part of the executive and legislative power to the Ridderschap (knightly estate) of each province, which consisted of the representatives of those families of the old feudal nobility.
The title Duke/Duchess (Hertog in Dutch) is no longer in existence in noble families of the Kingdom of the Netherlands in this day and age.