Question: Why would Henry do so many evil things to his own family?
Answer: Because he's nuts!
Question: Is this true that Mary Steenburgen was initially supposed to play Susan?
Answer: Yes. She had to drop out when production was delayed, and she was no longer available.
Answer: Henry apparently has what is called a "conduct disorder" - the term used for kids below the age of 18 engaging in what would be (and most likely will become) a diagnosis of sociopathy/psychopathy (antisocial personality disorder) when he becomes an adult. He is "evil", highly manipulative, self-centered, without remorse or other true feelings, and probably incapable of forming loving or long-term attachments. Many sociopaths are believed to have above average intelligence and make good imposters, capable of fooling others because they come across as "charming."
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