Margaret Merrow's mother was Josephine Gertrude Greusel (1861-1938). She was from a prominent German family of 19th century Detroit. Josephine was the daughter of Joseph Greusel (1820-1903), a German immigrant from Blieskastel, Bavaria and Margaret Doumonds (1828-1902) who was of Acadian and French descent.
Joseph Greusel was a postal carrier for the city of Detroit for more than 25 years. He would often walk more the 15 miles every day in performing his rounds. His brother, Josephine's uncle, Nicholas Greusel (1817-1896) was Union Brigadier General during the American Civil War. He saw action in the battles of Pea Ridge, Perryville, and Stones River. Another brother, John Greusel (1809-1886), was active in Michigan politics, serving in the State Senate and was a delegate to the 1872 Republican National Convention.