Jin's first appearance was within Tekken 3, where he is introduced as a boy "claiming to be Heihachi's grandson." According to official canon, during the King of Iron Fist Tournament 2, Jun Kazama and Kazuya Mishima were intimate, and Jun found herself pregnant afterwards. Jun disappeared into a remote mountain location where she raised Jin and trained him in her Kazama-Style Self-Defense fighting arts. Some time after Jin's 15th birthday, Jun was attacked by Ogre and disappeared. Grieving the loss of his mother, Jin swore revenge. He was then taken in by his grandfather, Heihachi Mishima, who began to train him in Mishima-Based Karate. In 4 years, the 19-year-old Jin then entered the tournament, defeated his grandfather, and destroyed Ogre in a fight. Jin then was gunned down by the Tekken Force and shot in the head by Heihachi. Jin's Devil Gene awakened and he threw his grandfather into a wall and flew off. (Source: Wikipedia)
