... and, prince does not always mean the 'son of a king'. On the Continent, there are princes in their own right: e.g., Monaco, Lichtenstein. German (and other Germanic languages have cognates) has Fürst. German also has Prinz. The former word is cognate with English first; in Latin princeps means literally 'first head'.

Old English had ęšeling for the 'son of a king'.

Ceci n'est pas un seing.