The Forgotten Soldier

[CJE]

His publisher (Laffont) wrote that his mother was German (Saxen) and that he volunteered at 17.

http://www.je-dis-non.com/article.php3?id_article=5

[Dénes Bernád]

Quote from his biography, taken from the site you just listed:
"Le jeune Guy, franco-allemand, n’avait a priori aucune raison de choisir l’un ou l’autre des deux belligérants."

I am wondering, how can one be French and German in the same time? Shouldn't he/she be either French, or German?

[CJE]

Must be an inheritance hard to live with. You have to choose your camp, not an easy decision in those troubled times.
Do you know that over 200,000 babies were born from a French woman and a German soldier during the war? They were called "fils de Boche" and had some hard times when they were young. But that's kind of OT.