I am also searching for Poels in Groningen. Though I don't believe I have run across your Jon Poel, we may still have names that link our trees. My great great grandmother was Henrietta Poel, born in Groningen on 9/20/1869 and married John Keizer. Her brothers were Klaas, Issac, Abel, Herman, Henry and a sister named Jennie. My Great great great grandfather was Jacob Poel born in 1830 in Groningen. He married Arrena Groenveld in 1859. Jacob's father was Klaas born 9/24/1799. he married Hendrikje Slager on 3/27/1828. If any of this is familiar to you, please write and maybe we can help each other! Thanks!