It seems like whenever a young 18th century prince was in need of some heirs a German princess of some sort came forth. But never a princess of Germany or the "Holy Roman Empire" as it was known. Instead it would be a princess of Bohemia here an electress of Saxony there.
Did you ever wonder where the heck all these modge-podges of countries came from? And were they really "countries?" Well they were imperial estates which were ruled by dukes, kings, etc. but they all feudally responded to the Holy Roman Emperor. This made for this sort of map hanging above the blackboard:Yuck.
But then again Europe was also a bit of a modge-podge itself. It's various empires and monarchies made for a much different map than what we have today. Take a look at Europe's borders in the 18th century here.