When Sirius was young, he loved doing all sorts of rebellious, unorthodox things that made him suffer dearly.
He remembered that the first time he was tortured by the Cruciatus Curse, he seemed to even see his younger brother's tears.
Come to think of it, their relationship wasn't so icy back then. Regulus was still like a normal child. When was it that things started to change?
Chapter 133