My g-grandparents, FRED NEUMAN & ROSE MOHRING NEUMAN came to US with some of my g-aunts and g-uncles in the early 1900s. They settled in Minnesota, where my grandmother was later born (1907) and remained until her death in 1994. There were always rumors between family members that we are of Jewish decent and they did not practice once they arrived into the US. Any ideas on how to substantiate this theory?