Aug. 11 (UPI) -- Demi Lovato surprised fans by joining the Jonas Brothers during their first show on the Jonas20: Greetings From Your Hometown Tour in New Jersey Sunday . Lovato, 32, had previously starred opposite Joe Jonas , 35, in the 2008 Camp Rock film and its 2010 sequel, and the pair performed songs from the movies , including "Wouldn't Change a Thing" and "This is Me," on Sunday. Lovato and Joe Jonas briefly dated in 2010. Brothers Kevin Jonas , 37, and Nick Jonas , 32, also appeared in