Although your sun signs may notbe compability, there are still other factors to consider when assessing compatibility in relationships. The method I use relies on the full natal chart of both parties. 

From the natal chart, if:

Your Sun, Moon, Venus or Ascendant is the same sign as their Sun sign and vice versa there is compaibility. For instance;

 

My Sun Sign is in Libra and my husbands Venus Sign is in Libra

 

This method works onthe following interpretation:

 

If your Sun Sign is the same as their Moon Sign:

Their emotional energy reacts the same as your basic nature; how you act outwardly is how they feel inwardly

 

If your Sun Sign is the same as their Venus Sign:

How you act outwardly is how they act within relationships and with whom they are closest with. You display the same energies as they display when with their spouse/lover

 

If your Sun Sign is the same as their Ascendant:

The mask that they show to the world is how you naturally are. They act to the world, the way that you are naturally.