Shakespeare's mistake

If the Duke of Milan, Antonio, as described in Shakespeare’s play The Tempest, had a son, then the entire play is completely overturned. The play has been running for centuries and nobody noticed? Who told Shakespeare the story that inspired him to write the Tempest, but also Romeo and Juliet? Where exactly is the Duke of Milan, Martino della Torre, buried? Why is there no grave of his in Milan while history says that is where he died? How come the oldest della Torre family coat of arms is in Cephalonia? Who is the Archangel holding a medieval shield in his right hand and a whip in his left hand? How did Bagrats find themselves in Cephalonia? Battles, coincidences, betrayals, secrets enter the warp of history and reveal a conspiracy that was broken many centuries later. A long journey for Emperor Charlemagne and King David. Meeting place: Cephalonia!