Just Who Are the Jonas Brothers?

Aug. 7, 2008 — -- Lately, the Jonas Brothers have been "Burnin' Up" the charts.

In advance of their live performance on "Good Morning America" Friday (click here for the full Summer Concert Series schedule), find out more about these rockin' New Jersey siblings.

The "Jo Bros" -- Kevin, 20; Joe, 18; and Nick, 15 -- got their big break last year as the opening act for Miley Cyrus. Kevin plays guitar, Joe sings lead and youngest brother, Nick, is known as the "president" or "musical mastermind" of the band. Cyrus recently admitted to Seventeen magazine that she was "in love" with Nick and that the two now-15-year olds dated for two years.

And these guys are entertainment veterans. Nick was in "Les Miserables" at age 8; Joe, the comedian of the family, was in "La Boheme" on Broadway; and Kevin, "the extrovert," has been in national commercials.

Now they are on their "Burnin' Up" tour through the first week in September and have an upcoming show on the Disney Channel called "J.O.N.A.S." In the program, the brothers will play rock stars who double as secret agents. "J.O.N.A.S." stands for "Junior Operatives Networking as Spies."

Kevin told ABC News in a recent interview that sudden fame is "an incredible experience. We constantly are, you know, kind of trying to pinch ourselves to wake ourselves up."

Nick agreed: "Even in the craziest moments, you'll catch us, like looking at each other and just smiling like, this is crazy."

But it seems as if they were made for fame. Nick told "GMA" that when he was 3 years old "I was telling my grandma that I wouldn't get off the coffee table because I was gonna be on Broadway and I had to practice."

Practice makes perfect for these brothers, who even have a recording studio on their tour bus, should the mood to create strike them on the road. They play their own instruments and write their own lyrics and own 29 guitars. Last year, they made roughly $12 million and just appeared on the cover of Rolling Stone.

And although their new album, "A Little Bit Longer," drops on Tuesday, they say they've already written five new songs for their next album.

The title track of "A Little Bit Longer" gives fans a look into Nick's battle with Type 1 diabetes. Just before his diagnosis two years ago, the already thin, 115-pound Jonas Brother lost 15 pounds from the disease. His brother Joe called it the "scariest thing ever."

Nick wrote "A Little Bit Longer" about his struggle to deal with the disease emotionally. He's performed the song on tour and said "just the fact that I can sing about it every night and tell my story makes me feel so honored."

Nick started a charity, Change for the Children, to raise funds and awareness for diabetes research and the whole Jonas family has become involved.

Their younger brother, Frankie, whom they refer to as the "Bonus Jonas," is 7 and already musically inclined. He already has his own band, but according to their Web site, the Jonas Brothers hope that when he gets older, he'll consider joining them.

As Kevin told ABC News, "We have a saying, you know, 'living the dream, baby, living the dream.'" And the Jonas Brothers seem to be doing just that.