Joe and Nick Jonas Sing 'Lovebug' Together at SunFest & Cause a Jonas Brothers Fan Frenzy: Watch

Jeff Kravitz/FilmMagic
Nick Jonas and Joe Jonas attend the 2016 MTV Video Music Awards at Madison Square Garden on Aug. 28, 2016 in New York City.  

Jonas Brothers mania continues in 2018. Four months after Nick, Kevin and Joe Jonas made fans go crazy when they reactivated their Instagram account in January, Nick Jonas and Joe Jonas reunited on stage -- and yes, sang a JoBros song.

During Nick's set at SunFest on Saturday night (May 5), Joe made a surprise appearance to both support his brother and sing a little of the Jonas Brothers acoustic hit "Lovebug." Naturally, their JB duet had the crowd going wild, especially when they put their arms around each other before Nick engaged fans in a (very loud) sing-along.

Both Nick and Joe -- who was in town to perform with DNCE at SunFest on Sunday -- posted a picture of the special moment on Instagram, with funny captions for each shot. "Who let this guy on stage?" Nick wrote, while Joe quipped, "Shared the stage with one of my biggest fans yesterday. Love ya bud keep it up!"

Joe has been hit by the love bug recently, announcing his engagement to Game of Thrones star Sophie Turner last October. As for an official Jonas Brothers reunion, fans are still holding out hope -- but clearly the guys aren't shy about singing their old songs, so keep that hope alive.

Watch Joe and Nick sing "Lovebug" together below.