Almost certain you are a
My prefix is the 9th.
Hermit is the 9th Tarot card
A prefix of the prefix is a pronoun.
My infix is in many languages, but not in English.
miti means myth in Italian, Albanian, Armenian, Azerbaijani, Basque, Bosnian, Bulgarian, etc. (courtesy of Google Translate)
An infix of the infix is another pronoun.
My suffix is a pot.
tian: an oval cooking-pot
A suffix of the suffix is a masculine name.
Together, I beg for a dagger.
Hermitian is represented by a dagger symbol in mathematics
I doubled, that's the identity.
The identity could refer to the definition of the Hermitian transpose where a Hermitian matrix is a complex square matrix that is equal to its own conjugate transpose.