What do you think?

The Young brothers?
The Schenker brrothers?
The Wilson sisters?
The Wilson brothers?
The Van Halens?
The Allman Brothers?
Someone else I haven't mentioned?

Being a massive ACDC fan, I am going for Malcolm and Angus. Mal's riffery and Angus's wizardry take some beating

The Kinks.

Oasis (to some people anyway )

The Darkness (as above )

The Noles ( Not rock but Rik Mayall fans should get it)
They did a Rock song with Lemmy, Cozy Powell, Micky Moody and Bob Young though.

https://www.youtube.com/watch?v=LczdjBhMOaw

The Bee Gees (If they are classed as Rock)

I would go with ACDC though as well. Lets not forget older brother George who helped the band he was in the Easybeats and was the bands producer for a while.

The Voltaire Twins.

https://www.youtube.com/watch?v=Bw4vS9pqt1k

Ray and Dave Davies probably win this. Although Max and Igor Cavalera are in with a shout. Maybe

https://www.youtube.com/watch?v=Tpgo2GdHCpQ

Probably go with The Kinks.

A few others worth mentioning...

Radiohead.
The National.
Kings of Leon.
First Aid Kit
The Black Crowes
Van Halen

There's a few missed. If we're talking Rock n' Roll.

The Everlys for a kick off.

I won't mention "The Kalin Twins."

https://www.youtube.com/watch?v=G55yNWCnXTI

Got to say this is popular, over 600,000 hits on just this upload.

What about Jesus and Mary Chain?
Arcade Fire?
Sparks?