On Thu, 14 Jan 2016 18:10:22 -0500, Nicole Valicia Thompson-Andrews <[log in to unmask]> wrote:

>I have two sign languages that I've adding to my language family. One
>is a trade language and the other is used for the the mute, deaf, and
>in a large crowd. The languages are Shadrey and Tangelian. Can Shadrey
>be the Proto-language of Tangelian? In other words, its use as a trade
>and crowd language expanded to include the mute and deaf.

As Logan has said, the answer is yes, this makes perfect sense.

I write to point out something else a bit wonky in your question, though.  Namely, a "language family" isn't just any old group of languages that go together.  A language family is a group of languages related by linguistic evolution.  So if you have added two sign languages to your family of spoken languages, that means that you posit that at some point, a spoken language *turned into* a sign language, or vice versa.  Ordinarily I'd say that's impossible; it has never happened on Earth.  However, given that I see you are intending to have some strange new method of language acquisition in your world, perhaps this is possible.  E.g. could someone have taken the "knowledge needle" that contained a spoken language and altered it into a sign language while leaving the grammar alone (mutatis mutandis), or vice versa?