This article from the 8/24/08 edition of the Colfax Record indicates that Christianity once had same-sex ceremonies akin to marriages:

Prof. John Boswell, the late Chairman of Yale University’s history department, discovered that in addition to heterosexual marriage ceremonies in ancient Christian church liturgical documents, there were also ceremonies called the “Office of Same-Sex Union” (10th and 11th century), and the “Order for Uniting Two Men” (11th and 12th century).

These church rites had all the symbols of a heterosexual marriage: the whole community gathered in a church, a blessing of the couple before the altar was conducted with their right hands joined, holy vows were exchanged, a priest officiated in the taking of the Eucharist and a wedding feast for the guests was celebrated afterwards. These elements all appear in contemporary illustrations of the holy union of the Byzantine Warrior-Emperor, Basil the First (867-886 CE) and his companion John.

Fascinating stuff.  The article provides quite a bit of detail.  This was the first I had heard of this.  It does present a challenge to the claims of contemporary Christians who abhor homosexual marriage because the concept of marriage has “always” involved one man and one woman.