Who is Dennys Murry from Many Waters and what is their importance?

Dennys is one of the identical twins. He listens to his family as they talk around him and he has a keen understanding of science due to conversations with his parents. He is very close to his twin brother. Dennys is practical and knows how to use his mind to work through tough situations such as when he is stuck in a different time in a different climate. When he and his brother become separated, he meets some nasty men who abuse him. He recovers in Naoh's tent before rejoining his brother. Dennys is fifteen years old and attracted to Yalith.