The alleged Marianne (Schwab) Rothschild could possibly be a distant cousin. Marianne was born in the same region as Schwab's family. It is written that Eugen Wilhelm Schwab and Erika Epprecht are Schwab's parents, archives, however, tell us that his mother is Emma Gisela Tekelius Schwab (NÉE KILIAN).

Emma is his real biological mother who was Jewish, making Schwab, according to rabbinical law, a Jew. But Schwab never mentions her and praises his non-biological mother, Epprecht, who had relatives who worked in a limited, indirect capacity for the nazi party for a short time.

That M. Schwab is possibly related, marrying into the Rothschild surname, but she is not Klaus' mother and we don't know how related she is distance wise.