Adelphopoiesis, or adelphopoiia from the Greek ἀδελφοποίησις, derived from ἀδελφός (adelphos) "brother" and ποιέω (poieō) "I make", literally "brother-making" is a ceremony practiced historically in some Christian traditions to unite together two people of the same sex (normally men) in church-recognized friendship. Similar blood brotherhood rituals were practiced by other cultures, including American Indians, ancient Chinese as well as Germanic and Scandinavian peoples. Documented in Byzantine manuscripts from the ninth to the fifteenth centuries, prayers established participants as "'spiritual brothers' (pneumatikous adelphous) and contained references to sainted pairs, including most notably SS Sergius and Bacchus, who were famous for their friendship."  In the late twentieth century, the lapsed Christian tradition gained notoriety as the focus of controversy involving advocates and opponents of secular and religious legalization of homosexual relationships in the West.
Adelphopoiesis in Christian tradition
The Russian polymath scholar, priest, and martyr Pavel Florensky offered a famous description of adelphopoiesis in his monumental 1914 book The Pillar and the Ground of The Truth: An Essay in Orthodox Theodicy in Twelve Letters, which included an early bibliography on the topic. Florensky described traditional Christian friendship, expressed in adelphopoiesis, as "a community molecule [rather than an atomistic individualism], a pair of friends, which is the principle of actions here, just as the family was this kind of molecule for the pagan community," reflecting Christ's words that "wherever two or more of you are gathered in my name, there am I in the midst of thee." Florensky in his theological exegesis of the rite described an overlap of Christian agapic and philic love in adelphopoiesis, but not eros, noting that its ceremonies consisted of prayer, scriptural reading, and ritual that involved partaking in presanctified eucharistic gifts 
Alternative views are that this rite was used in many ways, such as the formation of permanent pacts between leaders of nations or between religious brothers. This was a replacement for "blood-brotherhood" which was forbidden by the church at the time. Others such as Brent Shaw have maintained also that these unions were more akin to "blood-brotherhood" and had no sexual connotation.
"Same-sex union" or "brother-making"?
The ritual only gained popular attention in the West, however, after the late Yale historian John Boswell in his book Same-sex unions in pre-modern Europe, also published as The marriage of likeness, argued that the practice was to unite two persons in a marriage-like union. His theory was disputed by other academic experts on the issue, notably conservative UCLA historian Claudia Rapp, in a special issue of the Catholic scholarly journal Traditio (vol. 52) in 1997, which was devoted to a critique of his thesis. Boswell's work also was disputed by the religious community today descended most directly from that involved in the original practice, the Greek Orthodox Church, which regarded his work as a modern American cultural appropriation of its tradition, and translates adelphopoiesis as "fraternization," involving a chaste friendship. A similar translation of the term is "brother-making".
While many scholars criticized Boswell's findings, some agreed with him, including American Episcopalian scholars Robin Scroggs and William L. Countryman. Boswell gave text and translation for a number of versions of the "fraternization" ceremony in Greek, and translation for a number of Slavonic versions (Bratotvorenie), although Rapp and others disputed the accuracy of his translations. Boswell himself denied that adelphopoiesis should be properly translated as "homosexual marriage," but he argued that "brother-making" or "making of brothers" was an "anachronistically literal" translation and proposed "same-sex union" as the preferable rendering. Boswell's preference was problematic to Orthodox canonists, as well as scholars such as Rapp, who argued that it involved an anachronistically modern secular epistemology and anthropology, different from traditional Christianity. Boswell suggested a potential parallel to modern constructions of sexual identity, although the rites for adelphopoiesis explicitly highlighted the spiritual nature of the union in premodern Christian terms.
Boswell commented on the lack of any equivalent in the Western Latin Rite of the Roman Catholic Church, but the British historian Alan Bray in his book The Friend, gave a Latin text and translation of a Latin Catholic Rite from Slovenia, entitled Ordo ad fratres faciendum, literally "Order for the making of brothers". Allan Tulchin, "Same-Sex Couples Creating Households in Old Regime France: The Uses of the Affrèrement." in the Journal of Modern History: September 2007, argued that the ceremony of affrèrement in France joined unrelated same-gender couples in lifelong unions, who then could raise family, hold property jointly, and were in all respects the same as or equivalent to marriages in terms of law and social custom, as shown by parish records. These were not, however, contiguous with the earlier Eastern tradition, and not described in sexual terms in parallel to modern concepts of sexual identity.
- Patrick Viscuso, Greek Orthodox canonist. ""Failed Attempt to Rewrite History" New Oxford Book Reviews December 1994". Retrieved 2013-08-04.
- Florensky, The Pillar and Ground of the Truth', translated by Boris Jakim, Princeton 1997, p. 571-72.
- Florensky, The Pillar and the Ground of the Truth, p. 301.
- Florensky, The Pillar and Ground of the Truth', p. 327.
- http://www.eskimo.com/~nickz/qrd-eastern_orthodox/adelphopoiia.some-responses and http://www.melkite.org/Questions/M-4.htm
- Shaw, Brent (July 1994). "A Groom of One's Own?". The New Republic: 43–48. Archived from the original on May 7, 2006. Retrieved June 25, 2009.
- Fr. Evangelos K. Mantzouneas, Secretary of the Greek Synod Committee on Legal and Canonical Matters; English translation by Efthimios Mavrogeorgiadis, May 1994;Minor editing by Nicholas Zymaris. "Report on Adelphopoiesis 1982: "Fraternization from a Canonical Perspective" Athens 1982". Retrieved 2009-02-03.
- "Reviewing Boswell". Fordham.edu. Retrieved 2013-12-04.
- Boswell, Same-sex Unions in Pre-Modern Europe, p. 298-299.
- hina genontai pneumatikoi adelphoi hyper tous sarkikous (Boswell translation: "that they be joined together more in spirit than in flesh"). Greek text in Boswell, Same-Sex Unions, p. 316, n. 198.
- Allan Tulchin, "Same-Sex Couples Creating Households in Old Regime France: The Uses of the Affrèrement." Journal of Modern History: September 2007
- Gay Marriage: Reimagining Church History, First Things