It is my understanding that Franz Schreiber's son holds dual citizenship, between Germany and Finland.
I don't know how old he is now, but I have been led to believe that he owns a book store in Helsinki. I tried using the internet to find him, googling book stores in that city, but I drew a blank. I don't know if it's because his name isn't on the internet, or I just didn't know how to navigate through Finnish sites!
It would be quite interesting to talk to him, I think. What has he managed to save of his father's? Letters from the front, perhaps?
I've also thought of trying to get him to authorize an English version of Kampf Unter dem Nordlicht. I can think of about a dozen people I know that would buy it!