What other form of marriage was used to join two enslaved people?

The form of marriage that was used to join two enslaved people is known as contubernium. This arrangement was an informal union between two slaves, which did not have the same legal recognition as the formal marriages of free citizens. Contubernium allowed enslaved couples to live together and form familial bonds, but it was not sanctioned by Roman law in the way that the marriage of free individuals was.

In contrast, coēmptiō and confarreatio are forms of legitimate marriage that involved specific Roman legal rituals and were reserved for citizens, thus excluding enslaved individuals from being able to participate in such ceremonies. Usus is another form of marriage among free citizens that also includes the element of cohabitation but does not apply to the context of enslaved people. Hence, it is contubernium that accurately reflects the unique situation of enslaved individuals forming a partnership.