Although they started out as mere teens, the Titans have gone on to become one of DC's premiere superhero teams. Composed largely of former sidekicks and even once seen as a "junior Justice League," their ranks also include heroes who are unaffiliated with other characters. At the end of the day, however, all Titans represent the concept of legacy and growth.
Source：https://www.cbr.com/titans-justice-league-better-ranked/
