Georg August, Graf von Erbach Schönberg

Source: http://www.royaltyguide.nl/families/erbach/erbachschonberg.htm

Georg-August (1691-1758) became count of Erbach-Schoenberg in 1748. By 1820, the basis of promogeniture was instituted. In 1903, the then count was made a member of the Upper Chamber of the Grand Duchy of Hesse ; he also received the title of prince with the qualification of Durchlaucht, Serene Highness. An interesting footnote into the way these matters are regulated in Germany is that this title applies to all members of the family that are the issue of an "equal" marriage. An equal means one to someone of the same rank. Any male member of the family, who is considered to have married beneath him, loses his privileges. Readers should be under no illusion that these rules are necessarily in the process of being relaxed. Many of the royal families of Germany have seen several members "demoted" on these grounds.

Source: gothainternational.eu/Erbach-Schoenberg.pdf