Erwin is a complete jerk. That's basically all there is to him. He's a very broken character, but still a jerk. He is a character in Steampunk and is the brother of Octavia. When he was 16 his parents died and he took over their position of captain on their pirate ship. When he was 22 he murdered Gwen's parents because they didn't give him permission to marry their daughter. This, needless to say, caused Gwen and Erwin to break up. Regardless, over the course of Steampunk they reunite, date again, have a child and get married before Gwen tragically dies.
Erwin's jerkiness continues when Octavia dies. After a bit of sulking he starts laughing hysterically because it dawned on him that he didn't have to take care of her any more. Finally he only had to associate with who he wanted to associate, but then Gwen died and left him with the baby so he got what he deserved. HAHA! Jerk.
Among his countless other offences, events such as kicking a cat across the room come to mind.