There is no original documentation, but many sources list the first wife of Johannes Keim as the sister of Isaac DeTurk. Most sources name her as Katarina; one lists her as Bertha. Two non-primary sources are quoted in "The Family of Ada Rose Comer," by Ida DeMay Wilson, 1985, St. Helena, CA, as saying that Johannes' first wife was Katarina DeTurck. "American Ancestry: Giving the Name and Descent, in the Male line, of the Americans Whose Ancestors settled in the United States Previous to the Declaration of Independence," Vol. VII, published 1893, page 222, claims Johannes Keim's first wife was Bertha deTurk, sister of Isaac deTurk.

It should be noted that the church records found in Europe for Isaac DeTurk's siblings show neither a Katarina nor a Bertha. However, Johannes' first wife, regardless of who she was, was likely born about five years after those church records end.

Because of secondary sources, and because it seems to fit, I've assumed Johannes' first wife was a sibling of Isaac deTurk.