Petr Ginz is not only a boy, a son, a student, a brother, nephew, grandson, person. He also is a Mischling - the Nazi designation of someone of mixed "blood" - One parent, a Jew. One parent a Roman Catholic. Their child is a Mischling. See a Nazi Certificate for this category at Lotte's story at timewitnesses.org/english/2npreviw.html. A child of mixed blood. See also "Nazi classification for Germans of mixed race" at ://www.holocaustresearchproject.org/holoprelude/mischlinge.html/
Each degree of Mischling carried with it with different places and times for going to life or death. Definitions and consequences, Nazi, SS, Nuremberg Laws. See en.wikipedia.org/wiki/Mischling. Petr and his sister.
His sister's recollections of what it was like to be a Mischling, and what it meant, (Chava Pressburger, who edited his diary) are in the introduction at the site here, www.guardian.co.uk/family/story/0,,2103166,00.html. She discusses the Mischling status, and their degree.
With a Jewish father and non-Jewish mother, Petr's sister writes that the children were allowed to stay home until 14, and only then were sent to the concentration camps. So, other children - full-blood Jews - could be sent earlier. Petr's father, a Jew, only was sent to Theresienstadt toward the end of the war. A delay-dispensation of the marriage. His mother, an Aryan, remained home, and survived, as did Petr's sister, Chava Pressburger See www.guardian.co.uk/family/story/0,,2103166,00.html.