It’s the Bonus Jonas Brother, Frankie!
That kid you saw before is Frankie Jonas, aka the Bonus Jonas! While he's not an official member of the Jonas Brothers, big bros Kevin, Joe and Nick always make sure that Frankie is in on the fun. He has gotten to appear in a number of their Disney features, including a recurring role on their hit sitcom 'Jonas L.A.' Additionally, the Jo Bros bring Frankie onstage whenever they can to join in a couple of sing-alongs. Seriously, how awesome is that? We love the entire Jonas clan and how tight-knit they are!
Watch a Clip of Frankie Acting With His Big Brothers on 'Jonas L.A.'