I finally found out how the Pohlmann-Holzgraefe family fits into the family tree. There's only one genealogy book which mentions the Holzgraefe family in the Family History Library in Salt Lake City. I thumbed through it once, but it didn't look like they were related. Now that I've delved into my German Ancestry, I've found the connection.
Caspar Heinrich Holzgraefe (*1732) had three sons. I come from the youngest son, Ernst. The middle son, Otto Heinrich Holzgraefe (*1760) married Anne Cathrine Louise Neimeyer. Together they had several children before he died in 1803. In 1805, she remarried to a man named Gerhard Henrich Pohlmann who took over the "Holzgraefe" farm. Since their marriage, nearly every record uses both surnames for the family: Pohlmann-Holzgraefe. I'll have to go back to the library and check out that book again to learn more and maybe get in touch with the author.
