the 2 signs generaly are but there is alot more too it like "thepoetsappho" says. your sun, moon, ascendant and venus sign should have the same polarity. (yin yang positive negative) as said here: http://astrolibrary.org/synastry-1/ on the same website you will find this page that describes the elements and plolarities of all the signs. now all you need is to find a free natal birth chart online for each of you. good luck!! http://astrolibrary.org/elements/
oh and that will just be a basic way to see if you guys will get along smoothly, it is not an in depth interpretation of both your charts. so dont think this is going to describe every little aspect of you guys' relationship. just a basic general compatability. there will be many other little details that have nothing to do with this generalized view.
if he knows astrology is fake then no way are you compatible if he actually believes in astrology....then yes....you 2 are meant for each other
The Fish/Crab combo works really well. I've witnessed that being a very good match on a number of occasions over the years.
It is a big question, because the compatibility is necessary in relation also and for that it is good idea to consult the professionals through Online astrologer