I have a lot of information on Jacob and all the Jenneweins of Cincinnati.He was born in March 1855 in Cincinnati, married Ellen Grace on July 6, 1880, and died on Mary 26, 1922.
His father, Peter Jennewein, was born in the village of Fehrbach in 1816 (as were Peter's parents Matthew Jennewein and Salome Wuerz).
His mother, Louise Kirschner, was born in the same village in 1815 (as were her parents Joseph Kirschner and Elisabeth Schier).
Jacob's parents immigrated to the US aboard the ship HOWARD on June 11, 1852, with their two oldest surviving children:Elisabeth (who married Frank Koeter in Cincinnati and lived on Vine Street) and Peter (who was a tanner married Anna Gatting).Jacob also had a younger sister named Anna.
Besides the four children you list for Jacob, there is also one named Mary Elisabeth (born 10/17/1885 and died 11/24/1885).
Anna Edna, your great-grandmother, was born on February 5, 1894 in Cincinnati and married on November 25, 1915 to Charles H. Schmidt.
It does seem like Ellen Grace and Jacob Jennewein separated after the children were born.
If there's anything else specific that you're looking for, drop me a line.I have more info on your family.