William, the duke of Normandy: 1048 to 1060
Well, you should know how the story ends already. King Edward cannot raise an English army to campaign abroad in support of foreign interests. This seems obvious to everyone except you and your cousin. (Maybe it is a genetic disability, who can say?) When Edward finally dies early in 1066, Harold Godwinson becomes king by popular acclaim. Perhaps by then, you have accepted your self-induced fate of being only a mediocrity; perhaps also, you have become Harold's friend, and he awards you with lands in England. But you will, in any case, never be known to history as William the Conqueror.