I am Sagittarius and my boyfriend is Gemini do we have a future together?

Well opposite signs tend to attract. There may be cases where either Gemini or Sagittarius are being a little too honest with the other and can spur up some unpleasant feelings but your sun sign isn't the only indicator for a well rounded relationship. I would look up compatibility without birth times if you dont have the birth times for one or either of you. :)