The listing for Richard Markus has an error. His correct birthplace is Ostrow Wielkopolski, Poland, not the town that is listed. The city is here.
He was the son of Ephraim Abraham Marcus (1837-1926, died in Berlin). a glassmaker, and his second wife, Genette Ascher (1850-1927).
He had 10 half-siblings and one brother, who was Wilhelm Marcus (1883-1954, died in New York City), who was a labor and community leader in Berlin.
Various family members have their names listed as Marcus or Markus depending on the source.