Oppression
All his life, Francis had felt himself to be stifled, shoved into one box, one role, one way of being that he could not seem to break out from, or to allow more of himself to break through with. It was more than being asked to follow unsatisfactory rules, or to try to aspire to make himself "more" of something that he had not yet been able to mature into being. His life, from the day he first was deemed able to dwell among others, was one of censorship and restriction, for every moment of every day, he had to watch himself and his actions carefully, monitoring his every move and others' reactions to him to insure that he would pass their judgment of him as someone approximating normality.
Among his peers he must not be too quiet and reserved, or he would risk being a target of bullying for their perception of him as weak, but he must also not say too much or risk letting on the truth of his identity as distinctly different from them all- and if he allowed himself to be, infinitely more dangerous. Among his parents, when they were alive, and now with his brother David, after their death, he must censor his thoughts and feelings so as not to worry them, even as he floundered, unsure of who he was or where his niche in life would eventually be. And with the twins? If Francis lets weakness or uncertainty show in front of them even for a moment, it would give them that much more ammunition to use against him in the future, and that much more pleasure at his distress.
For the first fifteen years of his life, Francis drifted through life feeling a victim of his circumstances, a curse of genetics, always hiding his true identity, his true feelings, and most of all, the extent of damage he could cause, if he ever let himself break free of his feeble construct of normality. It wasn't until later, when he began to realize how much more satisfying it was to oppress rather than to be oppressed, that he was not made and was no longer willing to be someone else's victim, that Francis began to really relish his position in the world.
He was meant to be the oppressor all along.