What is the relationship between Bruno, Gretel, father and mother in The Boy in the Striped Pajamas?

The most
evident answer is that the relationship between all four characters is that they are a family,
the central family, in Boyne's novel.  They are all linked by blood and the relationship they
share.  As a family of four, they are the center of the narrative.  On a more symbolic, the
German family might be seen to represent the different aspects of German society during the
Holocaust.  Father is a believer in Nazism, representing the significant part of German society
that embraced Hitler's ideology and what it meant.  Gretel is one who becomes infatuated with
the power that accompanies Nazism, not fully aware of its implications.  The mother of the
family struggles between the support of her husband and the need to shelter her family from what
she knows is wrong.  Bruno could come to represent the portion of German society that stood up
to the Nazis.  While not significant in mass numbers, there were Germans, good Germans, who
recognized what Hitler was doing as wrong and stood up, paying the ultimate sacrifice, because
of it.  I think that this might be where the relationship between the family members can come to
represent more than the central characters in the Boyne novel.