Who is Robin Harper from The Lottery Rose and what is their importance?

Robin is Molly's youngest son. He is mentally delayed, and many people cannot understand what he is saying. When Paul was alive, Robin would rely on his older brother to help him. After Paul's death, Robin feels trapped within himself. It does not seem like anyone else can connect with him in the same way. All the boys at Georgie's school love Robin because of his sweet and kind demeanor.