Can You Make a Polygamous Oath?
If it really *fit* the purpose of the Oath, I'd let you stunt a three-way wedding. Or even four way. I mean, I know some solid polygamous triples in RL, and then there's Aramis, Athos, Porthos, and D'artagnan, who … qualify in a way that few PC groups do. But I suspect that the ritual is designed for exclusivity.