Graham's Journal (2006)

Eleven year old Graham Brady doesn't understand emotions. His sister, Morgan Ashley, is exactly the opposite; she feels everything, known for being friendly and outgoing to everyone around her. But with Graham for a brother, her natural kindness is short-lived. Deciding that his sister is far to weak to make it through life alone, Graham conducts a series of exercises to induce sociopathic behavior in Morgan Ashley and make her numb to what he calls the hell of living. Over the course of a few months, he narrates his harsh endeavors, documenting their results in his ratty old journal every step of the way, until innocent Morgan Brady has become just like him...and worse.