This question is asking about the brother and sister relationship that exists between Gretel and Bruno in the book The Boy in the Striped Pajamas. The relationship could probably be described as "cordial." Gretel and Bruno are not antagonistic toward each other, but they could hardly be described as best friends. This is a shocking disappointment as they are the only children outside the fence. Bruno and Gretel are both lonely characters, yet they don't spend much time interacting with each other. Gretel mainly serves as a source of information for readers and Bruno. She is the older, wiser, and more knowledgeable sibling, and that could be why Bruno seems so young. He's extremely ignorant of what his father is doing and why the pajama people are behind the fence. What's also frustrating about their relationship is that Gretel does begin to learn more about the war and the camp, yet she doesn't share much of that knowledge with her brother. Instead, she uses it to further separate herself from her kid brother, Bruno.