CryBaby Lane (2000)

Andrew (Jase Blankfort) and his older brother Carl (Trey Rogers) enjoy listening to ghost stories that the local undertaker (Frank Langella) tells them. One night he tells the tale of a local farmer whose wife gave birth to Siamese twins, one being good natured while the other was clearly evil. The farmer, ashamed of them, kept the twins locked in their room. Eventually the twins got sick and died together, so the farmer sawed them in half and buried the good twin in a cemetery and the bad twin in a shallow grave near the house. Later, Carl and his friends decide to hold a séance in the cemetery where the good twin is buried, but they unintentionally awaken the bad twin instead. Gradually, he possesses nearly everyone in town and it is up to young Andrew to stop him.