Tonpa mentions Amori and his brothers as regulars of the Hunter Exam. During the First Phase, Satotz's marathon, he and his brothers aid Tonpa in driving off some of the weaker contestants, such as Nicholas, showing that they've known Tonpa for some time, and have likely worked together with him before.
During the Fourth Phase of the exam, Imori stalks and attacks Killua in order to claim his badge. However, Killua easily takes his badge then overpowers and holds him hostage to force Imori and Umori to surrender their badges. Killua then throws two of the brothers' 3 badges into the woods since he doesn't need them, failing the trio. At the same time, he is being hunted by Hanzo who mistakenly receives Imori's badge instead.
While Gon is training on Greed Island, Amori and his brothers attend the 288th Hunter Exam, only to be easily knocked unconscious together with the rest of the candidates in the First Phase by Killua. Seeing the tremendous gap in abilities between Killua and themselves, despite Killua being much younger than them, they decide they'll never retake the Hunter Exam.