There appear to be matches to your research found in the local resource: "Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950). There are currently about 50 Broetzmann entries in the data.
My index entry for a Wilhelmine Broetzman (d. 1910) says her maiden name was Streich -- that's what the obituary says anyway; there were also multiple family death notices.
Indexing Milwaukee's German newspapers since 2007 ...
Gary Rebholz, compiler/editor