I'm involved with Birthday Matcher (here) for a number of different reasons, but one of them is not about putting people sharing the same date and year of birth together for the purpose of relationship.  If you were partnered with your astrological twin, you would soon find that you cancel each other out.  Comments I've had are like 'He/she was nothing like me', or 'They reminded me of who I used to be', or even better 'I'm not like that at all-am I?'  Firstly, there's the idea that you need external stimulus in relationship to ingnite your template, and someone the same will only create stasis.  And secondly, there's the prince and the pauper syndrome, two babies born same moment, same space, but one has a privileged upbringing and the other grows up in the gutter, so their choice of relationship wil be different.  Environment, upbringing and conditioning play a bigger part of early life than the horoscope - the horoscope only really kicks in when you leave home, whether you're fifteen or fifty.  So share your birthday with your partner, but same day AND same year probably won't work.  UPDATE: Imagine meeting your twin, but brought up in a different continent and environment, and sharing with them your life experiences.  You may have nothing in common on the surface, but your responses to events and stimuli would be the same, or near as damn it.  Imagine how you could both grow as individuals with the benefit of each other's experiences.  Imagine the parties you could have.  I have a number of clients who share birthdays with celebrities, it's fascinating to see the similarities and the differences.