"Gottfried (1809-1884) Schmitz who married Mary Catherine Kertzman (1801-1869) ..."
Have you collected the family death notices for this couple from the local German papers? You won't find these memorials in the English language papers. These are some of the over 300 Schmitz entries or references I've indexed in "Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950). Maria's notices reference the names Holzhauer, Kastenholz, Grove.
Gary Rebholz, compiler/editor
Indexing Milwaukee's German newspapers continuously since 2007... helping family researchers find their ancestors among Milwaukee's 99%.