Sirius hadn't been the one left alone with their abusive mother and apathetic father for a year, Regulus had. He was just a child and had done what he had to to survive. And when Sirius came back from Hogwarts, full of admiration for his new friends and new life and Regulus just no longer fit into anymore.

But more importantly, here, this place, Sirius was the one rejecting him all over again. Not Regulus. Well, not that first night.

"I'm not the one pushing anyone away."