Hello to any who read this, I have in the meantime found the hometown of my Gottlieb Koch, whom I still believe to be the same person working as a miner in the 1860 census in Ontonagon County. He came from Pfaffenhofen, Oberamt Brackenheim, Wuerttemberg, Germany and was born 18 Sept 1831 to parents Johann Michael Koch and Sophia Toberer.
I now believe the other two Kochs I mentioned are not related at all-- Leopold and Franz Koch came from another part of Wuerttemberg, Munderkingen.
So far I only know of Gottlieb's older sister emigrating to the US, Sophia Barbara, b 1814, married to Johannes Koch, who emigrated in 1868 to Detroit, MI.
Thanks for any further information on any of these.