Wikipedia (our most used tool) describes protomartyrs Sergius and Bacchus relationship as controversial, ranging from greek "erastai" (lovers) to the close brotherhood bond called "adephopoiia". However, in an article published last month in The Irish Times, Jim Duffy takes the couple and goes on along the controversial lines drawn by late Prof. John Boswell:
"Boswell found records of same-sex unions in such diverse archives as those in the Vatican, in St Petersburg, in Paris, Istanbul, and in Sinai, covering ering a period from the 8th to the 18th centuries. Nor is he the first to make such a discovery. The Dominican Jacques Goar (1601-1653) includes such ceremonies in a printed collection of Greek prayer books."
This issue is of course much controversial, and according to Catholic Dogma, when The Pope speaks on Doctrine he's the Voice of God on earth, thus whether traditionally some homosexual marriages have been accepted into the Catholic Church, what's clear is that nowadays such unions are definitely forbidden. However, there is a number of christian churches friendly to gay unions, not necessarily catholic.
I'd like to end this short note linking to a web site which deals with Homosexuality in History: "People With a History: An Online Guide To Lesbian, Gay, Bisexual and Trans* History".
EDIT: John Lauritsen reviews Boswell's book "Christianity, Social Tolerance and Homosexuality" in a critical manner to say that while Boswell depicts an idilic landscape of Catholic first centuries. There are interesting references in his critic: the philosopher Philo Judaeus and emperors Theodosium and Justinian. The review is really worth reading.