As a student at Hogwarts, Sirius was well-known for being a troublemaker, and once mentioned to Harry that he, James, Lupin, and Pettigrew "were all idiots." He once stated that he had never been appointed a prefect as he always spent too much time in detention with James. Sirius is protective of Harry, but also encourages him to take unwise risks and sometimes - inappropriately - acts with him as he used to with James. On this, the author commented that "what Harry craves is a father." Rowling has stated that though she likes Sirius, "I do not think he is wholly wonderful." According to her, despite being brave and loyal, Sirius is also reckless, embittered, and "slightly unbalanced by his long stay in Azkaban." When asked if Harry has a godmother, Rowling replied that "Sirius was always too busy being a big rebel to get married."
Unlike his parents and brother, Sirius detested the Dark Arts and did not believe in the so-called purity of blood. Rowling has said that Sirius has also proven to "be very good at spouting bits of excellent personal philosophy, but he does not always live up to them." This primarily has to do with his treatment of Kreacher the house-elf; because Kreacher was a reminder to Sirius of the home he had always hated (and also due to Kreacher's parading of the attitudes and views of Sirius's parents), Sirius is hateful to Kreacher and consistently mistreats him. This in turn comes back to haunt him, as Kreacher eventually betrays Sirius to Voldemort, leading to Sirius's death. Rowling has also stated that unlike Lupin, who is the same age as Sirius and appears more mature in nature, Sirius never really grew up, as he was placed in Azkaban during his early twenties and therefore had not had a very normal adult life. Despite all of this, Rowling states that Sirius's "redeeming quality is the affection that he is capable of feeling. He loved James like a brother and went on to transfer this attachment to Harry.