Who is Simon from The Field Guide and what is their importance?

Simon is Jared's twin brother. He doesn't share Jared's anger problems because he spends his energy catching pets and researching animals. Simon loves to read, but he is less aggressive than his brother in trying to figure things out. In general, he supports Jared's quest to uncover what is going on with the creature in the house. His feelings and thoughts, however, are often discounted by his mother.