Corin, or Corin Thunder-Fist, as he is later known, is the twin brother of Cor, or Shasta, the sons of King Lune of Archenland. Corin is the younger twin, and therefore is only second in line for the throne, although when Cor is abducted by Calormenes as an infant, Cor is made King Lune's heir, a position he does not relish since he enjoys being free and independent, unencumbered by the responsibilities being a king would demand. In 1014 NT when Corin was 14, he is taken under the wing of King Edmund of Narnia and his siblings, who include him in their activities and even offer to make him a knight of Narnia. Corin accompanies a delegation from Narnia to Calormen, where he gets into a fist-fight with a boy in Tashbaan when Queen Susan is insulted. When he makes his way back to the king's palace at the end of the day, he is surprised to find Shasta there, masquerading as himself. Corin is surprised at the similarity between them and the two boys become fast friends. He helps Shasta to get out of the palace and later escapes to Cair Paravel secretly along with the other Narnians to escape imprisonment. When news arrives that Anvard is being attacked by Rabadash and his men, Corin travels with a group of Narnians to aid in the fight. Despite his father's express wish that he should not fight in the battle, Corin forces Shasta to disguise himself and they both join the battle anyway. There, Corin fights bravely and makes his father proud of his courage, despite being rebuked for his rashness. When it is revealed that Shasta is Cor, Corin's long-lost older twin brother and therefore heir to the throne of Archenland, Corin can't hide his pleasure at the fact that Cor will be king instead of him and will have to shoulder all the responsibilities, while Corin will be able to have all the fun of being a prince. Corin grows up to be the best boxer in Archenland, earning himself the name "Corin Thunder-Fist", and is counted among the faithful at the Great Reunion in Aslan's Country.