A soul mate is someone from a soul group,someone with whom you are friends with in this life or others
A twin flame is the other half of your energy.You only ever incarnate once with your twin.They retain a little of your own energy be it the Masculine or Feminine part,thats what causes the attraction. You will only ever incarnate together on your last cycle on earth to grow together when you are brought together by the universe. It is when you have balance in the feminine and masculine in each of you
That is when " THE TWO BECOME ONE "
it has nothing to do with a marriage here on earth.It is about the reuniting of you and the other half of your energy
From there you shall grow forever with your twin