I'm Daniel Grotz from Cologne/North West Germany, but born and grown up in Stuttgart in the South West Germany. Unfortunately, I only know about my ancestors back to the end of 19th century. They used to live in the Swabian Alb near Stuttgart. My Great Grandfather was the organ player of the famous Hohenzollern Castle about 100 years ago, as far as I know. And most of the Grotz families are still living in this area (even in Stuttgart are around 25 Grotz'). So I think our branches are originated in Swabia.