["Children on the Ara Pacis," 9 BCE]
[Photographed by isawnyu, Source: Flickr]
While monogamy might have been the ideal in these relationships as in marriage and concubinage, particularly for the female partner, not everybody followed it. A study of inscriptions in Rome referring to concubinage and other de-facto marriages found nine that where one person had more than one contubernalis. Yet another lists a woman as wife to one man and contubernalis to another. Most probably refer to consecutive relationships, but there is evidence in at least the last one to suggest the possibility of concurrent ones.
The greatest area of concern for moralists and jurists alike were relationships between free women and slave men, which both inscriptional and legal evidence suggest were not uncommon. Since in Roman society, the male partner was supposed to be of higher status and wealth, such unions were discouraged. Late imperial jurists attempted to suppress them. There are always those who go against such pressures, and there enough examples of lower class free women in contubernium with male slaves even after these laws were put in place to suggest that such measures were ineffectual at best.
Additionally, there are numerous examples of freewomen, often freedwomen or the daughters of freedpersons, entering into relationships with male slaves who had risen to positions of power under rich masters. It would have been an attractive proposition for some women, but for those who held to the prevailing ideals of gender and status, such unions created a paradox. The man held greater power and wealth, but until he was freed, his partner had the higher status.
*For the curious, this breaks down to con (with) and taberna (hut, booth, or inn). It is sometimes translated as “cohabitation,” but as that word also describes one of the conditions of marriage in Roman law, I use the Latin term to avoid confusion.
Evans-Grubbs, Judith. "'Marriage More Shameful than Adultery': Slave-Mistress Relationships, 'Mixed-Marriages', and Late Roman Law." Phoenix 47.2 (1993): 125-154.
Rawson, Beryl. "Roman Concubinage and Other De Facto Marriages." Transactions of the American Philological Association 104 (1974): 279-305.