Hang in there, I'm going somewhere with this.
Dear Ex, I know I'm the last person you want to hear from. It's been years since we were an item, and you have a new life now. Let me assure you that I am not trying to change that. I'm writing you because of some bad treatment that my brother has reported suffering at your hands. First let me say that I understand that I am not a very good guy. To complicate matters, I was absolutely terrible for you. That having been said, it is not fair to punish him for the bad things that I did to you. You have successfully driven me out of your life, and even got many of your friends and family to abandon me as well. Fair enough, I probably deserve that. My brother does not.