The members of Gen 13 inherited the Gen-factor from their parents who were all part of Team 7. While part of Project: Genesis, their powers manifested. They escaped from Project: Genesis and formed Gen 13.
Gen 13 was created in 1994 by writers Jim Lee and Brandon Choi and artist J. Scott Campbell. Their intention was to create a younger team that was "less angry" and "less bloodthirsty" than other superhero teams that were popular at the time.
Visually the team is heavily inspired by Jim Lee. However, J. Scott Campbell gave the team a younger, manga-inspired look that proved popular.
Originally the comic was entitled Gen X, but Marvel objected due to the similarity to its popular X-men series and its upcoming title Generation X. The creators decided to change the title to Gen 13.
The team roster remained the same throughout the first continuing series: (Caitlin Fairchild, Roxy Spaulding / Freefall, Edmung Chang / Grunge, Sarah Rainmaker, and Bobby Lane / Burnout).
In an alternate universe, Caitlin Fairchild led a different group of super-powered teens: Janelle Moorhead, Gwendolyne Matsura, Hamza Mansour Al-Rashad, and Ethan York.
In the Wildstorm reboot, the members of the original Gen 13 team were again brought together by and escaped from a shadowy government agency.
Freefall and Rainmaker leave on the Carrier with the Authority, and Grunge joins up with the Wildcats. Fairchild and Burnout merge with Gen 14: Breakdown, Ditto, Runt, Hardbody, and Windsprint.
Major Story Arcs
The Original Gen¹³
International Operations started a "government internship" for gifted youths, taking place in an isolated training facility. Following the manifestation of Caitlin Fairchild's powers, she fled the complex with Roxy Spaulding, Grunge, Sarah Rainmaker and Burnout. The project was revealed to be a gathering of the gen-active progeny of Team 7. With the help of John Lynch, the kids finally escaped.
The group retreated to La Jolla, California, and officially formed as Gen¹³ under Lynch's mentorship. They opposed IO and their ultra violent counterpart DV8. (Gen¹³ loosely refers to the 13th generation of Americans. Team 7 had been part of a project called Gen 12.)
The team spent a lot of time delving into Team 7's past to learn more about themselves. Fairchild and Freefall learned they were half-sisters and Lynch was revealed to be Burnout's father. Also during this time, Freefall and Grunge began to date, while Rainmaker revealed herself to be bisexual.
The team was lured to an abandoned I.O. facility where they were used to fuel a Gen-factor bomb that unleashed a blast of raw extra-dimensional energy, with the side effect of releasing their powers as disembodied patterns of Gen-factor resonance which grew in power devastating Southern California and threatening the entire universe. Gen 13's allies, The Mongolian Barbecue Horde, discover that the environmental anomalies have been caused by the manifestation of Gen 13's powers and use an I.O. Gen-factor Extra-dimensional Energy Transmission Nullifer to nullify their energy patterns. In the process, Fairchild is translated into a living reality distortion (or "Gen-upload": the process by which human personality is encoded into a Gen-factor) and becomes in essence, a god.
Volume 3 - Reboot
Fairchild was the only survivor and mentored a new Gen¹³ team, effectively taking Lynch's role. However, this team existed in an alternate reality. The rest of the original Gen¹³ team was revealed to be alive and, after a little time-travel to avoid the detonation that 'killed' them, the reunited group returned to the mainstream Wildstorm universe.
Worldstorm - Reboot
After the events of Captain Atom: Armageddon, the series went through a soft reboot. The team's origins were all retold, updated, and modernized-- losing some of the tell tale 90's aspects that had been aging badly as time went on. They were all created by a corporation called Tabula Rasa (an I.O. government subcontractor), under the leadership and sadistic genius of Dr. Cross. They are the 13th generation of artificially engineered and enhanced beings created for the private use of Tabula Rasa's anonymous and incredibly wealthy clients. This is revealed to the group when they are forcibly taken from their families-- who are really just Tabula Rasa employees. The teens however escape the clutches of Dr. Cross and Tabula Rasa.
After escaping from I.O. through one of their own teleporters, the Gen 13 kids find themselves flung into Wildstorm's future where a great disaster has befallen the Earth. Disoriented and confused by this new development, the kids set out to discover what happened and how they will survive in this harsh new world.