This story is amazing. I love how in-character you've kept Sirius (young-of-mind and impulsive, even after Azkaban, and cocky and in desperate need of human contact and affection, and guilt-ridden) and Aberforth (gruff, so gruff! and somewhat-defensive, and practical, no-nonsense-y). Love the way you've used Aberforth's profession to create space for these characters to find companionship.
Even if it is instigated by Aberforth's meddling brother.