In "The Sea of Monsters" by Rick Riordan, Tyson experiences an overwhelming sense of joy and excitement upon realizing that Percy is his brother. This revelation makes him giddy, as if he has just received an incredible gift. His constant laughter and disbelief reflect his innocence and the deep longing for familial connection that he has yearned for.

Despite Tyson's enthusiasm, Percy feels the complexities surrounding their relationship. He understands that the bond of brotherhood comes with its challenges and responsibilities, indicating that their journey together will not be straightforward. This interaction highlights the themes of family and identity that are explored throughout the story.