User blog comment:Imperial Wyrm/Dragon Ball GT: A Hero's Legacy review/@comment-15906818-20150823022918/@comment-5718774-20150823025434

The characters were extremely underdeveloped. They could have explained a little bit what happened to the other Z-Fighters and what Goku Jr's origins were (he could be a clone or reincarnation of Goku maybe). Vegeta probably trained hard and went to the Dragon Realm to join Goku. Trunks eventually became head of Capsule Corp and a successful businessman and scientist. One of his kids or grandkids married someone who was surnamed "Leigh" (Vegeta Jr's mother is Bulma Leigh). Mr. Leigh, Vegeta Jr's adoptive father, is head of Capsule Corp. Goku Jr and Vegeta Jr were probably clones created to replace the original Goku and Vegeta. Gohan became a brilliant scientist and eventually died of old age probably around 30 years prior to A Hero's Legacy. Most Z-Fighters died of natural causes, but Tien becomes the new Turtle Hermit after Roshi goes to Other World, weary of his title. Korin and Dende are still alive at the time of A Hero's Legacy (so is Popo of course). Yajirobe died long before A Hero's Legacy, probably a few years after Omega Shenron was defeated, from a heart attack or something (Yajirobe does make cameos in GT). After Krillin died, Android 18 deactivated herself to join him in Other World, but they had descendants through their daughter Marron. Their descendants forgot about the Z-Fighters and blended in as normal Humans. Pan had probably been married sometime before A Hero's Legacy, but became a widow. After her kids, who were normal Humans, grew up, she later adopted Goku Jr as her grandson.

^ What I think happened before A Hero's Legacy