Germany,Pennsylvania,South Dakota, Illinois

I am looking for a family who came to this county from Germany and was first in Pennsylvania where at least three children were born: William, b. June 1857; Fredrick, born about that time;and Edward H. Lahman born May 1861.On William's marriage record it lists Fredrick Lahman and Mary Hage as the parents.I have been unable to find them in the 1860 or 1870 census records. I suspect that perhaps they went by other first names or something - or maybe someone misspelled their last name on an index.They list the place of birth as Warren, Pennsylvania for Edward H. but that could be Warren County Penn., or Warren, Franklin Co. Penn.Edward and William were in South Moline,Rock Island, Illinois in 1880.From there they seem to have gone to Brown County, South Dakota. Any ideas?