Seeing a marriage in your dream means commitment, harmony or transition.
You will undergo an important developmental transitional phase. It may also represent the unification of formerly separate or opposite aspects of yourself.
In particular, it may represent the union of masculine or feminine aspects of yourself. Dreaming of a proposal of marriage, suggests that some situation will take a turn for the worse.
Dreaming that you are getting married to your ex, suggests that you have accepted aspects of that relationship and learned from those past mistakes.
Alternatively, it means that a current relationship shares some commonality with your previous relationship with your ex. However, you will not make those same mistakes.