Born in La Push, Washington
Seth is the younger brother of Leah Clearwater; his parents are Harry and Sue Clearwater. Due to his family lines, Seth's parents always knew that he might some day become a shape-shifter to protect their tribe from vampires. However, it came as a shock to them when his older sister phases instead of Seth. So much so, that his father suffers a fatal heart attack. (In the movie "New Moon", Harry dies from a heart attack because of the vampire, Victoria.) Upon witnessing his father's death, Seth phases immediately.
Although saddened by the death of his father, Seth accepts his new lifestyle much easier than Leah. He feels that his new powers are a gift instead of a curse. And while Seth is still immature and childish at times, he is very optimistic and remarkably kind.
During the battle with the newborns (new vampires), Seth fights alongside Edward Cullen against Riley and Victoria. After that, they become good friends, and Seth looks up to Edward. Seth also has respect for the Cullen's, as he admires them for their "animal diet". It helps him to see them more as people rather than vampires.
Because Seth idolizes Jacob Black, he follows Jacob when he leaves Sam Uley's pack. He and his sister both join Jacob when he forms his own pack. Seth is known to have the best hearing out of both packs.