Well I found quite a bit of information but it raises more questions than it answers.

In the Index to Cincinnati OH Death Records 1906-1908 I found Charles Schuster, JR [implying his father was also Charles Schuster] age 79 yrs, 5 mo, 12 days, born Germany, died 1-15-1908, buried in Spring Grove Cemetery.

BUT Spring Grove burials are on line. Charles parents aren't listed but he is listed as Charles Schuster, SR. and her parents are listed as Jacob and --- HENSZLER. http://springgrove.org/sg/genealogy/sg_genealogy_home.shtm

His wife's name is the real fly in the ointment. I found a record of burial for their son, John Schuster at Vine Street Hill Cemetery:
John Schuster, age 85 yrs, 5 mo, 6 days - died 4 April 1942, born in Cincinnati, Spouse: Lena Pfadt, Parents: Charles Schuster and Mary HENCHLER

Restored Hamilton County Marriage Records 1850-1859 shows the marriage of Carl Schuster to Maria HENSLER, 21 Sep 1851 in St John Unitarian Church (12th & Elm) and that supposedly comes from LDS film 1510039. (This record can be found on www.familysearch.org but the name of the church isn't given.) This church's records are on film at the library, I can check to see if there is anything further next week, but those old records seldom give parents. I can also look for an obit, but again the parents aren't usually listed.

You might try writing or calling the Blegen Library. Before death certificates were issued, towns, cities and counties kept their own records. Cincinnati's records are kept in the Rare Books and Archives department of the Blegen Library. It's the only other place I can think of that might give his parents.
University of Cincinnati
Archives & Rare Books Dept
PO Box 210113
Cincinnati OH 45221
Phone 513-556-1959

Good luck to you! If I find more next week, I'll let you know.