What would become the Titans started with Beast Boy hanging out with Robin and Batgirl during the "super friends" era in 2003.
After the JLA was founded in 2004, Robin and Batgirl were a bit miffed that they couldn't join due to their age, so Bruce Wayne pocketed up some money to build a "clubhouse"/training center for them, that also gave Beast Boy and Victor Stone (who had just become Cyborg) a place to crash. Raven showed up soon thereafter, needing friends and heroes to ally with to stop her father. Within the first year, Starfire also joined.
Batgirl was shot that summer and went into a coma, so Robin became part-time about the same time Terra showed up. The team finally broke up after Terra's death. But some members of the JLA still believed in the program, so Oliver Queen partnered with Bruce to sponsor an expansion for the next generation.
