My cousin who is 94 says that his father, Carl Zellmer,had a half brother whose name was Gustav Zellmer.Gustav is supposed to have come from Germany on a ship called the De Elba and settled in LeSieur, Minn.
Carl's parents were Carl Zellmer and Elizbeth Betin'. Elizabeth was born in 1846.Carl is said to have immigrated when he was 8.
Doesn't really sound like the locations match but the names do. I have some other sibling names if you think there is any connection.