In Rick Riordan’s The Sea of Monsters, Percy Jackson’s half-brother is named Tyson.
Tyson is a young Cyclops and the son of Poseidon, which makes him Percy’s paternal half-brother. Percy initially feels embarrassed by Tyson’s size, manners, and vulnerability, but their relationship develops into one of the novel’s emotional centers. Tyson proves to be loyal, brave, and highly skilled at working with metal.
The brothers travel together during the quest to find the Golden Fleece, whose healing power may save the magical borders around Camp Half-Blood. Tyson’s Cyclops abilities are especially useful because he can survive conditions that would endanger many human demigods.
Tyson is sometimes confused with other demigod characters in the series, particularly Luke Castellan and Ethan Nakamura, who are sons of different gods and are not Percy’s family members. The Sea of Monsters was published in 2006 as the second Percy Jackson & the Olympians novel.