Jason Grace is one of the main characters of the Camp Half-Blood series. He is the Roman demigod son of Jupiter and Beryl Grace and the younger brother of Thalia Grace.
Jason and Thalia are the first demigods to be full siblings and have the same parents, followed by Travis and Conner Stoll, who are an older brother and younger brother sons of Hermes, Castor and Pollux (Sons of Dionysus), and Nico and Bianca di Angelo, Children of Hades. However, their father came to their mother as Jupiter and Zeus respectively.