Thanks Carl, we don't know what Oskar's parents' names were, but are hoping to find a death certificate as we recently managed to find his date of death. He died in 1937 in Berlin, so again, I'm not sure if this record will have survived. But we'll have a look.
I don't know if he was recruited from Romania or if he was already further West by that time. He married a Lithuanian. If anything turns up I'll be back here probably with more questions.
Once again many thanks.