Where rulers get their power by inheritance because they are a family, they are a dynasty. Monarchs were very common in history. Many countries had a monarch in past centuries, but no longer have them. Some countries that still have monarchs have other leaders that actually have the power.
Monarchs tended to have monarchs of lower honour below them, e.g. a Empire could include several kingdoms, and a kingdom would have several duchies or principalities, nations would rarely include all titles, usually going from duchy to kingdom instead of duchy to principality to kingdom. Prince/Princess means 'Ruler of a Principality' and 'son of king/queen'. Some other languages have separate words for them.
|Grand Principality||Grand Prince||Grand Princess|
|Archduchy||Arch Duke||Arch Duchess|
|Grand Duchy||Grand Duke||Grand Duchess|
|The Simple English Wiktionary has a definition for: monarch.|