I am no expert on the Neumann history (my brother is). It's just that the names your're asking about are close to my family names.My grandfather was Rudolph Frederick Neumann born in Graz in what was then Prussia (now Austria). He moved to Australia and had a son(my father) Frederick Neumann, born 10 August 1906 in Brisbane.
There is also a Margaret Hughes in my family but she was on my mother's side of the family.But I'm no expert.
Is this worth exploring?If so, please follow up next week as I am on holidays touring at the moment.