Bruno cares for Leonhard and Leonhard cares for him too. Leonhard calls him dearest brother, and he also respects him due to his intellegence. Bruno is somewhat jealous of Leonhard because Leonhard's naivety allows him to come up with solutions that Bruno never thought of.
Bruno argues a lot with Licht and this maybe caused by the differences in their personalities and their ways of doing things. Despite their differences, he cares a lot for Licht and Licht cares from him too. For example, when Licht told Bruno that he hated him, he felt that he did something wrong and wanted to apologize when he came back. When Licht was staying out too long, Bruno wanted to search for him because he cares for him, even if Licht doesn't feel the same (that's what Bruno thought).
Bruno seems to be in agreement with most of what his older brother Kai says. At times when he is fighting or arguing with licht, Kai comes to settle things in between them. Bruno along with his brothers, was really supportive of Kai when he was struggling to socialize with the royal staff. There was this one time when Bruno and Kai were attending military academy and bruno was being subjected to bullying by his peers, but he tried to keep the fact hidden . However Kai began to notice that Bruno is hiding something, leading kai to be concerned for his younger brother. When Kai found out the truth behind what was troubling his brother, Kai flew in to a rage and got engaged in a violent fight with Ralf Von Fuchs, thus resulting in kai being suspended from the academy. Shortly afterwards due to growing rumors, both Kai and Bruno were withdrawn from the military academy. Bruno felt responsible for the resulting incident however kai assured him that everything would be fine and matters were later resolved.
Bruno looks up to his father and wants to be just as successful and great as him. This leads him to work really hard in his studies so that one day he could be a worthy candidate to the royal throne. He is determined to make his father proud.
All that is known about the queen is that she was very loving and affectionate towards her children. Bruno is said to hold resemblance with his mother.
Leonhard is protective of his sister. When Heine pretended to be engaged or married to Adele, Leonhard was going to stop that from happening, and he wants her to marry someone worthy( as shown in chapter 15).
When Bruno was younger, he felt that he was inferior to Eins and never thought that he could catch up to him. This caused him to study and work hard to become great. He respects his brother but finds him scary in a way.
At the beginning, Bruno did not believe that Heine would be a good tutor for him because he didn't go to college, and there was nothing else that Heine could teach him. After testing Heine in various fields of skills, he saw the brilliance of Heine and calls him master. He thinks of himself as Heine's apprentice.