I have had a bit of break through for for!!
I found Gerhard's parents' marriage certificate. The key information translates as:
Charlottenburg II No. 133 of 1905
28 March 1905
Aloysius Bauch, worker/labourer [Arbeiter], b. 6 July 1876 Wadang, Kreis Allenstein, Ostpreussen [now Wadąg in Poland], of Spree Strasse 1
Son of Joseph Bauch, Arbeiter, and Anna born Kazmarck, both resident in Recklinghausen
Selma Günther, nurse [Krankenpfleger], b. 4 June 1876 Stassfurt, Kreis Calbe, of Spree Strasse 1
Daughter of Martin Andreas Heinrich Günther, bricklayer [Maurer], (deceased) and Johanna Christiane born Arndt, resident in Stassfurt
On the second page of the marriage cert there is an annotation which translates as:
Son born registration Nr. 160 / 1907 Berlin-Wilmersdorf
Married Wilmershaven Nr. 455 / 1940
The Berlin directories recorded the following:
1907 Alois Bauch, Portier [porter/doorman], Berliner Str. 130, Berlin-Wilmersdorf
1910 Alois Bauch, Hausdiener [house servant], Oberberger Strasse 21, Berlin-Wilmersdorf
1915: Alois Bauch, Gastwirth [innkeeper], Luisenplatz 7, Berlin NW6
1922: Alois Bauch, Maschinist [machine operator], Hannoversche Strasse 6, Berlin NW6
The birth registers for Wilmersdorf do not form part of the online collection on ancestry, which explains why you cannot find a record for Gerhard and his siblings.
Justin
I forgot to mention that a 'begläubigte Ablichtung' is a copy of a document which has been certified as authentic. One would only need such a copy to support a legal claim of some sort.