On June 18, 1155 Pope Adrian VI crowned Frederick I Holy Roman Emperor at St. Peter's Basilica. The Romans begin to riot, and Frederick spent his coronation day putting down the revolt. Suppose Frederick I is killed on his coronation day.
His sons: Frederick V, Duke of Swabia; Henry VI, Holy Roman Emperor; Frederick VI, Duke of Swabia; and Otto I, Count of Burgundy are not born.
Who becomes the Holy Roman Emperor?