Brotherhood: Final Fantasy XV EP3 - Sword and Shield

Gladiolus's origins with Noctis are shown within the frame of a monster encounter that turns into a friendly contest between Noctis and Gladiolus. Initially seeing him as a spoiled, self-centered child, Gladiolus's opinion is changed drastically when Noctis helps keep Gladiolus' sister Iris out of trouble by taking the blame for going outside the Citadel grounds with her. The two formed a close bond, which became a firm friendship by the events of XV.