Everything you know is wrong

When Charles Xavier was five years old, he worshiped his father. When he was eleven, he learned to loathe his abusive stepfather. When he was sixteen, he gave up any claim on the family fortune just to escape. At twenty-four, he's moved away from home into a crappy, standard-issue graduate student house, and gone through his degree program with his best friend, Moira, by his side.
He's adjusted. He knows who he is and where he comes from and what his future holds. At least, until a stranger in a bathrobe shows up in his living room, having used his shower, eaten his lunch and, oh yes, broken in uninvited. Suddenly, everything Charles knows to be true about himself may turn out to be wrong, and his future and past both may be more dangerous than he ever could have imagined.
(aka the bathrobe fic)