Certain movements recycle old, long-debunked arguments, counting on folks not to realize that these arguments have been forgotten because they were without merit. One such argument is the idea that adelphopoiesis was an ancient form of same-sex marriage.
Let’s address the timing issue first. The rite of adelphopoiesis is apparently documented from the ninth to the 15th century among the Byzantines. Thus, this is not “ancient” in the sense of being something from the patristic or early church period. It’s medieval.
Second, we can acknowledge that the rite of adelphopoiesis has some similarities to a Byzantine wedding rite. Nevertheless, those similarities do not mean that the intent of the ceremony was to create a same-sex exclusive sexual union, analogous to the opposite-sex exclusive sexual union formed in a wedding.
The argument comes from John Boswell’s book, “Same-Sex Unions in Premodern Europe.” However, Patrick Viscuso (in the December 1994 New Oxford Review) debunked Boswell’s theory in a variety of way, primarily by noting the fact that Byzantine marriage process involved a lot more than simply a ceremony in a church.
Instead, as Viscuso explains, the term is best understood to be “brother adoption,” rather than anything analogous to a marriage. I won’t repeat all of his arguments, but hopefully reading the article will prepare you for handling this issue.