identical twin

:  being the same :  selfsame

:  having such close resemblance as to be essentially the same

:  having the same cause or origin

:  either of two offspring produced at a birth

:  gemini

:  one of two persons or things closely related to or resembling each other

:  born with one other or as a pair at one birth

:  made up of two similar, related, or connected members or parts :  double

:  paired in a close or necessary relationship :  matching

:  to bring together in close association :  couple

:  duplicate, match

:  to bring forth twins