This story is taking shape as it goes, I'm surprising myself with what seems to be flowing out of it. You are right that relationship between the brothers and their terrible childhood is a very interesting and complex study; I mean forcing children to participate in the abuse of other children, especially their own siblings is just monstrous, truly evil in my view. However, I'm going to leave that side of it out of this story. See comment below. Mycroft is just going to be in denial about everything...