I think: Manfred tells the knights that Alfonso the Good, dieing childless in the Holy Land bequeathed his estates to his grandfather, Don Ricardo, “in consideration of his faithful services.” I take this to mean that Don Ricardo was somehow in the service or at least some sort of companion, lower in rank, to Alfonso and not a blood relation. At least that is Don Ricardo’s story. As I see it, Manfred is not related to Frederic marquis of Vicenza who is the nearest of blood to Alfonso and therefore the rightful heir. Besides being a villain, Manfred wants Isabella married into his line to help legitimize his claim to Otranto. :D

I have a different scenario for how Don Ricardo became the Prince of Otranto. To prove that he intends no treachery towards the three knights he gives his ring (my gage) to the principal knight saying “your friends and you shall enjoy the laws of hospitality.” I figure that this gage must be the symbol of the realm just like in many other stories—the notes (Penguin Classics) say that a gage is “something of value deposited to ensure the performance of some action, and liable to forfeiture in case of non-performance, a pawn, pledge, or security.” Ok, finally to my theory: Don Ricardo takes the ring from Alfonso in the Holy Land before or after death and returns to Otranto with it and makes his claim as prince by its authority and keeps it by force. :D