One of the Tsars also married a member of the last Byzantine dynasty. Though a member of the dynasty with a stronger claim sold the title to the king of France and also left it in his will to Ferdinand and Isabella, so the French and Spanish monarchs claimed it for a while too. You'd think monarchs with actual power would refrain from giving themselves fake titles over land they don't control, because it kind of calls into question the legitimacy of their other titles, and because it might give ideas to people who want their land. But most of them seem to love giving themselves dozens of meaningless titles.