Ruy Lopez

Why is it that very few players play Qn-k2 in response to white's third move b-b5? Is it really better to allow doubled pawns?

1 e4 e5 2 Nf3 Nc6 3 Bb5 Nge7 is solid but passive. It is difficult to develop the king's bishop, usually via 4...g6 and 5...Bg7. Wilhelm Steinitz used to play like that.
There is no need to fear doubled pawns. That white loses the bishop's pair with 3...a6 4 Bxc6 dxc6 more than compensates the doubled pawns. That is why most white players retreat 4 Ba4 instead of taking.
The modern trend is the old 3...Nf6 the so called Berlin defence as championed by Emanuel Lasker.

I feel awful when my K side bishop is blocked and I can't castle.

With 6...Bg7 it is playable.
Also 4...Ng6 is playable.
However, black stands passive and the first mistake can be lethal.
Smyslov and Spassky have played it though, so it is definitely playable and it avoids all the theory of the mainstream defences.

I really messed up this thread. Sorry. I meant: for black's third move is GN-k7 viable?

I see you figured out what these means, pls share this information. :)

Qn-k2 (???) GN-k7 (???)

@Rise , @Sarg0n ,

thx, this is new to me, now i understand QN-K2, but Sargon answered with an example of KN-K2 and still, cant find what means GN.