I too am looking for BONN family. This is what I have, let me know if any of it fits with yours?
Johannes Bonn m. 1848 to Anna Weber in Guttenburg, Iowa Theodore J. Bonn b. 2/6/1854 in WI, d. 7/20/1908 m. Margret Mueller Henry John Bonn b. 5/7/1876 in WI, d. 10/11/1930 m. Mathilda Weidman, Groton S.D. Albert Henry Bonn b. 8/10/1902 in S.D. m. Evelyn Larson in S.D.