Do you have death dates for this couple? There are possible matches in "Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950). For instance was John an active member of the Turner's org. and sang in their choir?
There are about 75 occurrences of the name Trost in the growing index, and surnames referenced with Trost are Widerholt Ries Krejci Maurer Schulz Schultz Schaefer Bliesner Brahm Drost Prinz Reiff.
Gary Rebholz, compiler/editor
Indexing Milwaukee's German newspapers continuously since 2007... helping to access our historic German-American culture.