どちらも	3750494	99.9%
何方も	4699	0.1%

@@ -6 +6 @@
-<ke_pri>spec1</ke_pri>
+<ke_inf>&rK;</ke_inf>

Thanks, I think that works.

It's an English grammatical rule that "both" becomes "either" in negative sentences. But in Japanese, there's no such rule.
"私はそのふたごのどちらも知らない" literally means "I don't know both of those twins." It's only one sense in Japanese, but if we want to include "either", we'd have to do something like this.

@@ -20,0 +21,6 @@
+<sense>
+<pos>&exp;</pos>
+<misc>&uk;</misc>
+<s_inf>with neg. sentence</s_inf>
+<gloss>(not) either</gloss>
+</sense>

Tanaka:
私はそのふたごのどちらも知らない。  I don't know either twin.
これらはどちらも“意志未来”と呼ばれるもので、主語の意図が含まれています。  These are both called "future 
volitional" and include the intent of the subject.

I was happy with two senses. In the Tanaka sentences they're not really interchangeable. I 
think "either" should be included.

meikyo: "二つのものが両方とも。双方。「肉と野菜、─好きです」"

This isn't two senses. どちらも means "both" (両方とも). In English, there are contexts where "both" and "either" are more or less interchangeable, but どちらも doesn't have the "one or the other of two things" meaning. GG5 does have "either" as a gloss but perhaps we should leave it out to avoid confusion.
Meiyko gives the PoS as 連語.

@@ -17 +17 @@
-<pos>&adv;</pos>
+<pos>&exp;</pos>
@@ -21,5 +20,0 @@
-<sense>
-<pos>&adv;</pos>
-<misc>&uk;</misc>
-<gloss>either</gloss>
-</sense>