Stackable familiars

[Captnq]

So I get extra familiar.

I have three familiars of the same type. Don't matter what type.
I'm a generalist elf wizrad and I get that level that doubles the output of my familiar bonus.

I now have +6, +6, +6 to [X].

Do they stack? Can I have a wizard with +18 to say spot?
(and then the ravens all use aid another to give me an additional +2, +2, +2.)

[kitep]

Even unnamed bonuses from the same source don't stack.  So if the bonus is from having a familiar, I would say no, they don't stack, so no +18.

[linklord231]

I think three familiars would be three sources. 

[Maat Mons]

The extra familiar feat itself says the bonuses don't stack. 

[linklord231]

The extra familiar feat itself says the bonuses don't stack.

Ah, good point.  That's what I get for not reading the feat first.

Extra Familiar:
General
You have an additional familiar.
Benefit:  By taking this feat you get an additional animal familiar of a type described in the Player's Handbook (or this article, with the DM's permission).  This familiar can be the same type of animal as the first, or a different type.  Existing familiar feats apply to the new familiar.  So if you have the Construct Familiar feat, for example, the familiar you call can be a construct.  The sorcerer or wizard gains all the benefits of both familiars, but identical bonuses from multiple familiars don't stack. For example, a wizard with both an owl and a cat receives only a +2 bonus to Move Silently checks, not a +4 bonus. 
Special:  A character can gain this feat multiple times.  Each time you take this feat, you can call another familiar.