For a very long period, formal amatory unions, conjugal, elective and indissoluble, between two members of the same sex were made in Europe, publicly recognised and consecrated in churches through Christian ritual.
They were never identical to heterosexual marriages – in societies in which gender differences were so significant, how could they have been? – but were often implicitly or explicitly compared to and contrasted with heterosexual marriages, and were by no means considered to come off the worse for the comparison. Indeed, as partnerships entered into by individuals acting as autonomous agents out of love for each other, same-sex weddings are much closer to modern companionate marriages than the heir-centred, family-allying and often family-arranged marriages of former times.
http://www.lrb.co.uk/v27/n11/davi02_.html The term "same-sex union" used in the title of this book is a translation of a Greek phrase (adelphopoiia) which if translated literally would be rendered "making into a brother" or "adopting as a brother." The term is used in medieval Christian manuscripts written in Greek and Slavonic to identify an ecclesiastical rite. A representative prayer in such a rite reads as follows:
Merciful and loving Lord, who has made man according to your image and likeness, who willed that your holy Apostles Philip and Bartholomew become brothers, bound to each other not by nature but by faith and spiritually; as your holy martyrs Sergius and Bachus were worthy to become brothers, bless these your servants N. and N.; being bound together not by nature but by faith and spiritually, give them peace and love and oneness of mind. Remove from their minds all stain and impurity and bring it about that they love one another without hate and without offense all the days of their lives. May the Mother of God and all the saints intercede for them. All glory is yours alone, O God.
This prayer was accompanied by ritual actions in which the persons to be joined placed their right hands on the Gospel book and held candles in their left hands. At the conclusion of the rite they kissed the Gospel book, the priest, and one another.
Such rituals are found, in the main, in liturgical books written in Greece or the Balkans between the twelfth and sixteenth centuries. They are familiar to scholars of Eastern Christian liturgy and to legal historians, but are largely unknown to Western readers. This new study by John Boswell, a historian at Yale University, provides transcriptions as well as English translations (for the first time) of a representative group of these rituals and an interpretation of their meaning and historical significance. In Boswell's view these rituals for the binding of two males are equivalent to "heterosexual" marriage ceremonies and were used by Christian clergy in medieval Eastern Christendom to bless "gay marriages."
http://www.encyclopedia.com/doc/1G1-15822984.html