Need ideas for esearching great great grandfather (1880's Illinois/Michigan)

My great grandmother married a man with the last name Lowe and had one living child with him. I find her in censuses in the 1880 census living with her mother-in-law and husband (George Lowe) with an infant son who later dies. But my grandmother (Florence) who was born in 1880 is not listed in the household. My great great grandfather's will does not name my grandmother as his child and in his mother's will she leaves a bequest to their daughter, but not my great great grandmother. On her marriage certificate my great grandmother lists her father as "Edward Lowe" born in Illinois. There are a lot of clues that George Lowe was not my great grandmother's father- but she was born in the same year that her mother and George Lowe were married. There does not seem to be a brother in the Lowe family named Edward. I haven't had luck finding a birth certificate from my grandmother - though it seems very likely she was born in Michigan. The lost 1890's censuses are a bummer here. By 1896 my great grandmother is listed in a city directory as a dressmaker living in an apartment in Detroit (she would be 16). Her mother (widowed) is living with her younger half sister in an apartment nearby also listed as a dressmaker. Any ideas for me? How would you go about tracking down Edward Lowe?