Jan has the same origin story as her brother Jayce. Their planet was attacked by Zorathians. The Zorathians killed their parents and a vast majority of the population leaving them as orphans. Space Ghost rescued them both, during the invasion Jan and Jayce were cornered by a bunch of the Zorathians and were about to be killed when Space Ghost showed up and fought and killed their tormentors, Space Ghost then fought off the rest of the Zorathians and met his arch-nemesis Zorak in the process. Because Jan and Jayce were now orphans and his own wife and child had been killed, he decided to adopt Jan and Jace and train them as his sidekicks.
In Space Ghost Coast to Coast, Jan and Jayce sued Space Ghost for damages which include physically and mentally stunting their bodies.