Regulus is about to be sorted and stands on the side of the group waiting for his name to be called. Suddenly Sirius stands up and approaches Regulus and gives him potions to counteract the effects of the abuse from their parents.
Bellatrix yells from across the hall “get away from him you traitor” Sirius yells back without thinking because he is angry and frustrated “no!! because you know what cousin” he sneers “you will never have to understand what abuse we have to go through with our parents. At least your blood purist parents are nice, bitch!!”.
McGonagall intervenes before it can escalate “Mr. Black 2 point from Gryffindor and go back to the Gryffindor table please.” Sirius went back to his table grumbling, ‘at least I helped Reggie’ he thought ‘hopefully I can get him out of that wrecked house at the end of the year like I did’.