Oh Brother! I Slept with My Stepsibling!

A sheltered, poor teen (MC)  breaks the rules for the first time when she gets drunk at a prep school party and loses her virginity to  a stranger. While her mother and stepfather are looking for her, they die in a car crash. A guilty MC is adopted by her stepfather's rich and evil ex-wife only to realize that her one-night stand, is her stepbrother.