Some days, Sirius gets visits; in the beginning, he had so many visitors that they had to ask him, does he know this person, claims to have been at Hogwarts with him? or that person, from the Ministry? None of the names were friendly or familiar, and after his mother Walburga Black was let in—she had demanded, and is technically his blood relative—after he had them remove her from the premises and spent days reliving his childhood in a panic-induced stupor, Sirius asked Dumbledore to write a list of possible visitors, trusting that he will know who is still able and on their side. (Not that there are sides, now, what with the war over...)