Ezel is a man that is out for revenge, over the murder of his brother, and he is ironically he is calloborating with his enimies, to help get revenge for his brothers murder. And in the same time he is helping, one of his enimies get revenge over the her sisters murder, because he believes both are linked.
From what I understand he believes that he was the one who was meant to be killed, but his brother was in the place that he was supposed to be. so the person had killed his brother thinking that it was him who they'd killed, when actually it was his brother.