In this episode Vilgax states that Ben has been thwarting his plans for over a decade, which wouls imply that Ben was at least 21 during the events of Omniverse as the series starts when Ben is 10 years old. This is inconsistnt with this very website which sttes he is only 16 during the events of Omniverse so I'd an answer as to whether he is 21+ and this site is wrong or if he's 16 and this is simply huge mistake on the show's part.