A Jonas Brothers primer

Albums include their Columbia debut, "It's About Time" (2006), and three for Hollywood Records: "Jonas Brothers" (2007), "A Little Bit Longer" (2008) and "Lines, Vines and Trying Times" (2009).

Though they're mostly known as a trio, there's a fourth Jonas, Frankie, coming up.

Paul Kevin Jonas (II)

Born: Nov. 5, 1987.

Nickname: K2 (aka Kevin).

In the band: Lead guitar and backing vocals.

Dish: The most animated Jonas stage performer.

Romantic link: Recently engaged to longtime hometown squeeze, Danielle Deleasa.

Joseph Adam Jonas

Born: Aug. 15, 1989.

Nickname: DJ Danger.

In the band: Lead vocals, percussion, guitar, keyboard.

Dish: The "dream boat" Jonas (Disney Channel picked him to co-star in "Camp Rock" with Demi Lovato).

Romantic links: Country-pop star Taylor Swift (so 2008, though they're still singing about each other); actress Camilla Belle.

Nicholas Jerry Jonas

Born: Sept. 16, 1992.

Nickname: Mr. President.

In the band: Lead vocals, rhythm guitar, piano, drums, lead songwriter.

Dish: The "serious" Jonas is the band's main songwriter and is also a spokesman for diabetes, from which he suffers (Type I).

Romantic links: Exes include singer/actress Miley Cyrus and actress Selena Gomez.

Franklin Nathaniel Jonas

Born: Sept. 28, 2000.

Nicknames: Frankie, Bonus Jonas, Frank the Tank.

(Almost) in the band: Debuted in "J.O.N.A.S!" and will have a bit part in "Camp Rock 2: The Final Jam," expected to hit theaters in 2010.

- Jonathan Takiff

The pop-rockers hail from Wyckoff, N.J., and now reside in the Dallas suburb of Westlake, Texas. They're committed evangelical Christians. Father Kevin Sr. is a former Assembly of God minister, and they were homeschooled by their mother, Denise.