I have. I wrote a book, not very well written in hindsight, about twins.
One twin was good and one was very evil and cunning and smart. Often, he'd pass himself off as his brother and cause all kinds of havoc.
So as I wrote the good twin as the hero of this book who falls in love with the Heroine, enters the evil twin and his mind games.
When I began writing this story, I had a true solid understanding of these two characters. They were clearly defined and no mistakes between the two, but when I began writing them, something started to happen, when I laid my head down, in my darkened room, at bedtime. And no, it wasn’t the attack of the run-on sentences.
What happened was, as I contemplated what direction to take my story the following day, the evil twin would visit me.
“How do you know that your good twin is really the good one?” He'd stand in my door way and ask me. “How do you know I’m not pretending to be the good one? What if the good one really is evil underneath it all?”
He’d taunt me, but worse, he’d make me think. I began to doubt myself. "What if he was right? Am I writing the wrong story?"
The following day, as I tackled the next several scenes with those taunts in mind, I finished for the day and headed to bed. No sooner than I’d close my eyes, I felt his presence. As I opened my eyes, I’d see the twin standing at the foot of my bed.
“Don’t listen to him ( evil twin). I really am the good one. He’s tricking you to turn him into the hero of this book. He’s not redeemable, LaNora. You know this."
Eventually, I finished the story and kept the "Good" twin good and the "Evil" twin evil but not without writing a scene where he seriously gets his butt kicked. After I finished my book, I sat back in my chair and told my screen, “That’s for haunting me!”
(The above picture I found is of the male models-The Carson brothers)