Harry James Potter? No I'm Viola Irene Darkholme

There wasn't much Harry was certain of but there where certain facts of life he didn't question. He was the orphan son of James and Lily Potter, his only family hated him, he only mattered as the "boy-who-lived" not as Harry, and he never felt comfortable as himself. What happens when all of that is suddenly flipped upside down and everything he knew suddenly didn't matter? What's a mutant and why does being a girl make him so happy? Response to Whitetigerwolf's Mutant Son challenge