Eventually we figured out that David is Kyson's imaginary friend. He wants to take David to Bear Lake with us and I told him that would be fine as long as it was okay with David's mom. Of course David got permission to go with us and he apparently will be riding up with my mother a day early to greet Kyson when he gets there.
I don't know much about imaginary children, but I've heard rumors that it's a sign of intelligence, and I read that children who make-up imaginary friends are able to take on another person's perspective more easily, and tend to be more empathetic. After reading this, an imaginary friend makes sense to me for Kyson. He is one of the most intuitive kids when it comes to emotions of others. Maybe David will be a good thing after all.