Really? I thought Stephen King wrote one about someone who absorbed their "evil twin" and then the one twin became a writer and then the "evil twin" came back from the nether world to try and steal the main character's life.

Yeah I just looked it up she has a trilogy about twin girls.

Unlike both of those authors, I was planning on having the twins be different genders. So one consciousness wants to be and do boy stuff and the other wants to go do traditional girl things.(like shopping for cute shoes in the mall or something.)