Same-sex union will never be the same as marriage
The Catholic Church states that marriage is between a man and woman, united in the sexual act which can bring a child into existence.
No other relationship can do this. It is the essence of marriage. No other relationship can be called "marriage".
To refer to "same-sex marriage" is clearly self-contradictory. To say that one is equal to the other is a misunderstanding of the essential meaning of marriage.
It is obvious that no same-sex relationship can be truthfully said to be equal to the union of a man and a woman united in marriage, with the possible conception of a child resulting from such a relationship.
Anything else does not make sense.