Oscar Lang was born in 1895 in Privoz, which was located in the agglomeration of Ostrava in Moravia region in the Czech Republic. Unfortunately it has been appeared that in ancient archives from that region, only indexes remained. Those indexes shows only names of children plus the name of the father. Presumably Oscar Lang has been listed in those index as Oscar Fritz Lang, and the name of the father is listed as Ignaz or Ignatz. Those indexes shows two more children with the same father's name: Robert and Elise, possibly siblings of Oscar Lang.
Those indexes are to see by clicking at the following two links:
http://www.badatelna.eu/fond/1073/reprodukce/?zaznamId=1957&reproId=130255
and
http://www.badatelna.eu/fond/1073/reprodukce/?zaznamId=1957&reproId=130269
Source: Vladimir Bohinc, Nove Mesto nad Vahom, Slovak Republic and the editors of the Jewish Monument.