From the story, i can only deduce Navin as a normal guy, as normal as you, Ratobhaley. You have not really painted any picture of any psychological disturbance with Navin. You did talk about how your dad is an epitome of morality in Nepal and how your parents did an amazing job raising you as a single child. But nowhere i see Navin being treated badly or had any other psychological trauma. Being a child with 4 siblings is not enough evidence to turn him into a psychopathic killer. Yes stealing is definitely wrong but if that was enough reason for someone to resort to senseless violence, then believe me, we would have a lot more problems.

Well, you can just say that you woke up from your dream sweating and Navin was sleeping peacefully in the next room, then all of this was a figment of your imagination. Then you will have a problem of thinking of Navin as a killer than Navin himself who has no idea what goes inside your head :-)