Speaking of equality in marriage, the Church holds that marriage is a sacrament and hence indissoluble both by men and by women, indissoluble both by commoners and by kings.
In this regard, an article from 1972 by Joseph Ratzinger on the dogmatic-historical state of affairs and its significance for the present has recently been translated into English: On the Question of the Indissolubility of Marriage. Here are a few excerpts:
The marriage of baptized persons is indissoluble. This is a clear and unambiguous directive of the faith of the Church of all centuries, a faith nourishing itself from the Scriptures. It is a categorical directive, that is not at the disposal of the Church, but is given to the Church to witness and to realize; it would be irresponsible to give the impression that anything on this point could be changed. The “yes” of marriage in the Church participates in that definitiveness that in the definitive decision of God for man at the same time has become visible as human possibility. It continues the “decisive decision” of God for man in the decisive decision of man for man. Marriage is one of those fundamental decisions of human existence that can only be made completely or not at all, precisely because therein man as a whole is involved, as his very self, unto that depth where he, touched by Christ, transformed, is taken into his “I” opened on the cross and open for us all. This is what is meant when we call marriage a “sacrament”. . . .
. . . . Marriage is a sacramentum, it stands in the irrevocable fundamental form of the decisive decision. But this does not mean that the Communion community of the church does not also encompass those people who accept this teaching and this life principle, but are in a special predicament, in which they especially need the full communion with the Body of Christ. The Church’s faith will also thus remain a sign of contradiction: That is essential to it, and precisely by this fact it knows that it is following the Lord, who foretold to his disciples that they should not expect to be above the master, who was rejected by the pious and by the liberals, by Jews and by Gentiles.