You may not yet be in on the phenomenon created by 20-year-old Kevin, 18-year-old Joe and 15-year-old Nick. They opened for Miley Cyrus on her fall “Hannah Montana” tour to the delight of shrieking girls everywhere. Their song, “S.O.S.,” catapulted to No. 1 on iTunes. Their second album has sold more than 900,000 copies. And that’s just the beginning.

Earlier this month, the band became the youngest act to sign a deal with concert presenter Live Nation. The multimillion dollar, two-year pact includes promoting 140 shows in theaters and arenas worldwide by the New Jersey-based brothers starting Jan. 31 in Arizona.

“We know where we’re going to be at the end of 2009,” says Joe, incredulously.

While some may consider putting such big money behind a still-developing act risky, Billboard’s Ray Waddell calls it a smart move: “The Jonas Brothers are about as safe a bet as exists in the music business today,” he says. “This is a Super Bowl year for them.”

Indeed, the band’s three February shows at the Gibson Amphitheater in Universal City, Calif., set a record for the fastest sellouts in the venue’s 35-year history when the first two shows sold out in two minutes.