Clearly not the best article I’ve ever read, but you may find it useful nonetheless.
Here’s some logic for you: If Man and Woman can create a family (i.e. children) then they should be the fundamental unit of the family through marriage.
Most Men & Women can create children. I don’t know of once instance where a man and a man or a woman and a woman were able to create children.
Therefore, it follows logically: Only the combination of a Man and a Woman can create a family and therefore only a man and a woman can be married.