Two sons of Friedrich Wilhelm von Frankenberg-Ludwigsdorf lived in Wisconsin: Emil lived in West Bend (Washington Co.), and Ernst lived in Newburg (Ozaukee Co.). In 1867 they had a family reunion with their sister Helene. The event was written up in the Milwaukee's German newspapers and includes a biography of their father. According to the article, the brothers are known as "Frankenberg". Emil died in 1868, with an obituary in Milwaukee's German papers, probably the West Bend & Ozaukee German papers too. Ernst published notices about the sale of Emil's estate in the German papers. An online search shows references to Ernst Frankenberg and his store in Newburg.
"Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950).
Gary Rebholz, originator/compiler/editor, Milwaukee Wis.
Indexing Milwaukee's German newspapers continuously since 2007... and beyond 2013.