The blood between us
(Book)

Growing up, Adrien and his sister Grace competed for everything. It wasn't easy being the adopted sibling, but Adrien tried to get along; Grace didn't. When their scientist parents died, they drifted apart. In their senior year, they are both back at the boarding school where their parents taught. Life gets more complicated when Adrien starts to suspect that Grace might be stealing their parents' research and claiming it as her own-- or worse, that she was involved in their deaths. Adrien begins to wonder whether she's guilty and, if so, what he's going to do about it.