where is the family from? My family with the grunkemeyer/grinkemeyer, etc name is from Franklin County Indiana. My g-grandmother was Anna Grunkemeyer and had a brother by the name of Joseph with a father named John and grandfather of Henry. Take a look at the Rootsweb site for Franklin County. It has censuses for various decades. Its census index of 1870 has the family mispelled with a K. Let me know if this family sounds like yours. I have a handwritten copy of a obituary of Mary, wife of John.
On a side, still trying to find out the relationship between John and a Theodore Grunkemeyer. Also was this name originally with a German umlaut? Could explain the different spellings in English since the German sound is different from sounds in English