My Berg family line (among many others) holds a fairly standard, complex history for ordinary people of the day: but be prepared: these particular people are statistically most likely not related to you.
My gm Anna Bar Berg, last name at birth was Bar because at Anna's birth her mother provided her own last name as Anna's name of record: Anna's mother was Elisabetha Friederike Bär; Friede's father was Christian Bär a resident of Karlsruhe who died there. Frieda's mother was Rosa Bär (nee) Herrmann.
Anna Elisabeth Bär,1889–1980
Birth 25 OCT 1889 • Karlsruhe, Baden, Preußen; Death: 13 AUG 1980 • Middletown, Middlesex, Connecticut (or New Haven) USA
Anna's father was Josef Berg who legitimised her later, giving her the surname Berg ( so finding her birth record was a problem). She came to the US as Anna Berg. (My father was Rudolf Berg (adoptive name Hilse)).
Josef's father was unknown because Josef's mother did not have the man's name added to the record. His mother's birth name was Christina von Berg, as she showed on the birth record for all her four children, of whom only Josef survived.
Perhaps Christina's ancestors harbored a Christian von Berg among them (who later dropped the "von" as already being useless in that era ), but so far her father has become a brick wall. The recorded name of her father is Carl von Berg (source: Archives in Stadt Karlsruhe's); that said, he could have three other first names of record, after the fashion of his preceding generations).
I offer this because it casts a bit of light on Jan's and Helmut's comments and questions for you. They are simply trying to get a bit more specific to be helpful in searches. You can see from my example that more is needed. It took years for me to find this much.