Young Prince William was the firstborn son of Henry II of England and Eleanor of Aquitaine. He was born on the 17th of August 1153, but died after a seizure in April 1156. He was only ever given the honour of being the Count of Poitiers, a fiefdom belonging to his mother.
Having died at such a young age, there is no telling what kind of man he would have grown into had he survived. But would it be worth speculating on the future of the Plantagenet Angevin Empire if he managed to survive into adulthood?