Pre-history
A title associated with Kent first appears anciently with the Kingdom of Kent (or Cantware), one of the seven Anglo-Saxon kingdoms that later merged to form the Kingdom of England. The Kings of Cantware (or Kent) date back to about 449. After 825, when the Kingdom of Kent was taken over by Egbert, King of Wessex, Kent became a dependency of Wessex and was ruled by sub-kings, usually related to the Wessex rulers. The titular kingship became something like the heir-apparent's title, as Aethelwulf, Egbert's son, became King of Kent in 825. By 860, Kent lost its status as a kingdom, becoming absorbed into Wessex.
Read more about this topic: Duke Of Kent