One of the last things you might expect to burst the cynical bubble of indie rock would be Austin’s Brothers and Sisters . Yet this hippieish seven-piece, led by siblings Lily and Will Courtney, has found itself wowing black-clad teens and sharing the stage with bands like . . . And You Will Know Us by the Trail of Dead. The Courtneys’ adoration of sixties pop makes their music play like something straight out of the Wayback Machine: Despite its modern guitar slash, this is the sound of the Byrds, the Mamas and the Papas, John Sebastian, Alex Chilton, and a thousand genre-bending one-hit wonders. Fortunately (Calla Lily Music), the band’s sophomore effort, manages to keep Brothers and Sisters’ sunny pop from sounding sickly sweet. This is partly thanks to the arrangements, which retain the circuslike, cluttered atmosphere of the group’s live shows. But it also has to do with the songs themselves, the best of which (“Mason City,” “You’re Gone”) jangle without sounding like jingles. Armed with a boatload of hooks, the Courtneys harmonize effortlessly, and all of a sudden, it’s 1966 all over again. What’s not to like?