I always felt bad for Regulus - he was described as "soft" by Sirius, indicating that he couldn't stand up to the pressure from Slytherin and his family to become a Death Eater. I think he was sort of swept up by it, and tried to make things right later on. Would've been hard for both of them, knowing they were on different sides of the war, but I never see them as hating each other. More just feeling devastated that they weren't on the same side.
You always nail Sirius with his expressions and everything. I love that you do Regulus drawings. No one seems to do it, and you do a great job. I love the subtle differences between the brothers. Its really awesome.
This is really, really good! I like your interpretation of them! And I specially like how Regulus puts his hand around his arm (the dark mark, I suppose?). And you also managed to make Sirius look really handsome... This is the best pic of them I've seen for a long time. ^^