Looking for Information on Christina Elizabeth Doelker

I am looking for information on my great grandmother. I believe her parents were Killian Doelker b 1842 in Germany and Magdalena VonEpp born in 1850. They emmigrated around 1870. Christina married Walter Von Behren b. 12 July 1880, they had only 1 child my grandmother, Evelyn Von Behren. Any info on the Doelker side would be much appreciated.