Bros: O'Kelly, Ronald, Rudolph and later Ernie.
Active: 1954 to present
"It's Your Thing," "Fight the Power"
Of note: Jimi Hendrix was once their backup guitarist.
Bros: Don and Phil
Active: 1957-73, 1983 to present
Genre: Pop and country
Key songs: "Wake Up Little Susie," "All I Have to Do Is Dream"
Of note: They were among the first class inducted into Rock Hall of Fame.
Bros: Barry, Morris and Robin Gibb
Genre: Pop and R&B/disco
Key songs: "How Can You Mend a Broken Heart," "Stayin' Alive"
Of note: 1977's "Saturday Night Fever" is the top-selling soundtrack ever.
Bros: Michael, Jermaine, Marlon, Tito, Jackie and later Randy
Genre: R&B and pop
Key songs: "I Want You Back," "Dancing Machine"
Of note: Continued as the Jacksons after Michael's solo success.
Bros: Bill, Brett and Mark
Key songs: "So You Are a Star," "Rendezvous"
Of note: Bill is the father of actress Kate Hudson.
Bros: Howard and David
Active: 1968 to present
Key song: "Let Your Love Flow"
Of note: A Groucho Marx line inspired their Grammy-winning song "If I Said You Had a Beautiful Body, Would You Hold It Against Me."
Bros: Twins Gunnar and Matthew
Active: 1989 to present
Key songs: "Love and Affection," "After the Rain"
Of note: Their dad is Rock Hall of Famer Ricky Nelson.
K-CI AND JOJO
Bros: Cedric and Joel Hailey
Active: 1990 to present
Key songs: "How Do U Want It," "All My Life"
Of note: They used to be in the group Jodeci.
Bros: Taylor, Isaac and Zac
Active: 1992 to present
Key songs: "MMMBop," "I Will Come to You"
Of note: "MMMBop" was No. 1 in seven countries.