Creedence Clearwater Revival (Fogertys)
Prefab Sprout (McAloons)
Shack (Heads)
Crowded House (Finns, but Tim Finn was not a regular member)
Jackson Five (How come nobody mentioned this?)
Ira / George Gershwin (They were a songwriting team, rather than a pop group)
INXS (Farriss')
Screaming Trees (Conners)
Everly Brothers (duh)
Beach Boys (Wilsons)
Just to name 10 off the top of my head. Oh yeh, Stooges too.
Also, there's a group called the Walker Brothers, but none of them are called Walker, and they are not brothers.