Sometimes people call such a person a "claimant". The person may be an imposter (someone who is pretending to be someone else). Often they are pretending to be a prince or other royal person who is missing or whom people think is dead. However, they may have a genuine right to the throne. The word "pretend" comes from the French word "prétendre" (from the Latin "praetendo" lit. "to stretch out before"). It means: to profess, to make a loud statement. In modern English the word "pretend" means "to claim falsely".