Family of Fredericka ZEH GRAF (1843 - 1914)

I may have made a small crack in one of my brick walls this past week while traveling in Minnesota and being able to do some research there. I am looking for information on the parents of Fredericka ZEH, primarily more info on her father.

The following is "family history" with some confirmation from other sources. Fredericka ZEH was born in (Wurtemberg) Germany on 10 Jan 1843. She came to the United States with her parents in 1852 (unconfirmed) via New York, settling in Philadelphia. In May 1864 in Philadelphia, she married Emil GRAF (my wife's great-grandfather). He had been in the hospital there due to injuries instead of being with his unit at Gettysburg (most of which did not survive). Emil and his new bride went to his home in Marine Mills, Washington county, Minnesota. They lived there until 1879 when they moved to Nobles county, Minnesota. Shortly after the 1910 census, they moved to St. Cloud Florida, where Fredericka died in April 1914. She is buried back in Nobles county, MN.

Fredericka's mother was Christina B. ZEH, maiden name unknown. Also known as Christine B., her mother was born 25 Oct 1813 according to her tombstone (in Nobles county MN). She and two sons (Fredericka's brothers) moved to Minnesota from Philadelphia some time before the 1880 census. Her brother Charles T. ZEH was born 17 Mar 1851 and died 20 Aug 1899 and is buried in Nobles county also. Her brother Frederick (b. 29 Sep 1844) lived until Aug 1918. He is also buried in Nobles county MN.

Fredericka's father is a real unknown. Family history has stated that his first name was Frederick. He supposedly left the family while they were living in Philadelphia to "find a better place for the family to live" and was never heard from again. Lately, I have seen some indications that his first name may not have been Frederick, or at least he was known by some other names.

Now for some of the more recent discoveries. In the death records at the Recorders Office in Nobles county, the entry for Fredericka has an interesting entry in the columns for her parent's names. Listing her mother first, the entry is "Schermeyer & ___________ Zeh." I am guessing that Schermeyer may be Christina's maiden name. (I have not had much luck with any searches on this, but I have just started.) In the same record book, the entry for Fredericka's brother Frederick leaves the mother's name column blank and lists his father as M. ZEH.

Another discovery on this trip was an article on Emil GRAF (husband of Fredericka) in the "Memorial Record of Southwestern Minnesota" published in 1897 by The Lewis Publishing Co of Chicago. On page 218, it first refers to Fredericka's parents as Frederick and Barbara ZEH. Christina's middle initial was B, but this is the first time I have seen her referred to by this name. Later in the same paragraph it states "the mother [Christina] and other members of the family came to Mr. Graf's and she died at age of 76 years. She had five children, three of whom are yet living." This is the first mention of any siblings in addition to Fredericka, Frederick, and Charles.

I am looking for more information on Fredericka's parents, especially her father, and her two previously unknown siblings.