Matthew Chase

Matthew Chase is Fredrick Chase and Mrs. Chase's son and Annabeth's younger half-brother. His father is shown to confuse him with his brother, Bobby Chase.

History
He and Bobby are born to Fredrick Chase and Mrs. Chase in 90's. Because his half-sister Annabeth was a demigod there was monsters attacks, and when he was a baby, Annabeth ran away.

The Titan's Curse
He is seen playing with his brother, Bobby Chase when Percy, Thalia, Grover, and Zoë ask Mr. Chase, Annabeth's mortal father, for help. Percy looks at the Legos scattered on the floor and the cookies in the oven and decides it's "not a bad place".