If we follow Wiki policy then a man that did not rule should not be named by the title he did not hold In Aimones case specificly he neither ruled nor reigned All the people you listed have had a stronger position on their respective thrones than the Duke I am aware of all the examples you have brought forth but still I cannot think of a supposed monarch that was less of a monarch than Aimone Objectively speaking he really had little or nothing to do with that country