Gan and Tavis Williams are twin brothers that were born of a Vietnamese woman and an American soldier named Lt. Walter Williams. Originally conjoined twins, they were separated with magic. As children, they found themselves beginning to manifest superpowers. However, they had little control over these powers, and without an infusion of their father's blood, they would quickly burn themselves out. So, they took the aliases Thunder and Lightning, respectively, and set off to America to search for their father. However, they caused major disturbances in St. Louis in the process and engaged in battle against the Teen Titans. However, after their aims were revealed, the Titans decided to help the pair.
Months later, the Teen Titans and S.T.A.R. Labs were working on a cure for Thunder and Lightning's powers. At the same time, Raven, using her powers, discovered that their father was actually an alien who had crash landed in Cambodia six hundred years ago, and was currently being held hostage by the H.I.V.E. as they tried to exploit knowledge from him. When they located him, H.I.V.E. controlled the alien in a fight against Thunder and Lightning and the Teen Titans. In the end, Thunder and Lightning were forced to kill their father to protect their new friends. However, a blood sample from their father allowed S.T.A.R. Labs to create the cure that would allow Thunder and Lightning to control their powers.
Thunder and Lightning are the two characters in the Teen Titans episode, "Forces of Nature". They are spiritual brothers that like to cause mischief that leads to destruction. The Teen Titans fought Thunder and Lightning. Beast Boy convinced Thunder that what they're doing to the people and the town is wrong. Thunder and Lightning met up with a mysterious sorcerer (who was really Slade in disguise) and created a monster made of fire.
Finally, Thunder and Lightning realized that their "fun" was wrong. Lightning, thinking Thunder betrayed him angrily fought together. Then, Thunder and Lightning made up and created a rainstorm to extinguish the flame monster, putting it's reign of terror to an end. Then Thunder and Lightning apologized to the Teen Titans for what they've done.