The relationship that Thomas has with Chuck is very unique. Thomas is an alpha in the society in the Glade, whereas Chuck is at the bottom of the social class. Yet despite the odds, the 2 boys develop a special connection. while Chuck may occasionally get on Thomas's nerves, Thomas promises to protect Chuck. They love each other, even if it isn't explicitly shown all the time.
This relationship is comparable to the relationship between Ralph and Piggy from Lord of the flies. Ralph is Alpha in his society as well, and Piggy just like Chuck is at the bottom of his society. There relationship is similar in that Ralph although annoyed by Piggy does love him, and needs him. Just as Thomas does with Chuck. Just like Piggy, chuck dies at the hands of the antagonist, and his death is the end of any remaining order on the island. the same is true of Chucks death. Although Chucks death resonated on a much more emotional level then Piggy's death did with Ralph, both had a profound effect on the protagonist and the sense of order int he 2 novels.
When both of those 2 characters died, any final senses of order or salvation fades, and hope seems lost. Both figures seemed to bring hope to the situations, and with them gone, it creates a hopeless air to the novel. Also both characters death has a large impact on the protagonists, both main characters feel a sense of loss and emptiness after the death of their friends.