I stole Edward's identity to work with a scientist on the Red Stone, and continue my father's work. I want nothing more than to complete my father's dream, and will stop at nothing to do so-- I wont let anyone else take the credit for his work. While I might seem like a smart-aleck and poser, I have a caring heart, and, just like Ed, try my best to protect my younger brother. I also has a small amount of guilt for what my research as been doing-- not as big as my brothers, but it still shows.
Much to Ed's surprise, and horror, I am both a year younger than him, and about 6 inches taller. Even though I act all high and mighty, I still aspire to be like Ed someday, without having to steal his identity.