Complex sentence: Herbert "Spermwhale" Whalen is the oldest and--legitimately--the toughest of the choirboys--but, unlike Roscoe Rules, he isn't a bully.
Split into simpler sentences: Herbert "Spermwhale" Whalen is the oldest and--legitimately--the toughest of the choirboys. However, unlike Roscoe Rules, he isn't a bully.