The modern term for adelphopoiesis, a medieval Christian ceremony uniting two men (or less often, two women) in a bond similar to heterosexual matrimony. Although adelphopoiesis vows resembled
traditional marriage vows, they did not include a sanction of sexual relations between the couple.
For more information see John
Boswell, "Same-Sex Unions in Premodern Europe", New York,
Villard Books, 1994.