LOS ANGELES – Most young men can be forgiven for not knowing what they’ll be doing two days from now, much less two years. Not the three siblings who comprise the hit trio the Jonas Bros. The superstars-in-the-making have every day mapped out for the next 24 months.

If you’re not a tween/teenage girl or don’t live in proximity to one, 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.

Even the brothers admit they can’t wrap their heads around the Live Nation deal. “In a weird way, it’s humbling,” Nick says. “People think you’d get a big head about it, but it’s like, ‘Wow. Someone would do this?'”

All this success comes after the band got off to a rocky start. Its debut album came out on Columbia in 2006 to little fanfare because their primary champion, Columbia president Steve Greenberg, had departed the label by the time it was released. The band soon parted ways with Columbia and signed with its current home, Hollywood Records. (The album, “It’s About Time,” is now a collector’s item with an asking price of up to $299 on Amazon.com)

The comparisons with Hanson are inevitable: like Hanson, these three brothers write their own songs and play their own instruments, giving them more credibility than the average boy band. (The Jonas Bros. even name drop Hanson in their song “That’s Just the Way We Roll.”) While their songs are solid power pop, the tunes possess more of a rock edge than those by many of their contemporaries.

The tour is the first step toward global domination that Hollywood Records parent, The Walt Disney Co., has provided in the past for such acts as Hilary Duff, Cyrus and the cast of “High School Musical,” all of whom have enjoyed platinum and/or multiplatinum success. Though mainstream radio has been largely resistant to these acts, there are signs that the Jonas Bros. will break through with new single “When You Look Me in the Eyes,” which is already receiving airplay on pop stations in New York and Los Angeles.

“The only way to get onto pop radio is to make records with broad appeal. They have begun to do that,” Greenberg says. “This is different from being big in Disney’s proprietary media, where super-serving the core young audience is all that matters.”