I've since found out that, although they identified themselves as Germans, they came from "Petrikau", the German name for Piotrków Trybunalski, Łódź Voivodeship, Polska. Their youngest know son, Fritz/Fred, was born apparently born in "Rosenberg", the German name for Olesno, Opole Voivodship, Polska. At the time, this was Congress Poland, a Russian satellite.