The next question to consider is the age at marriage of the slaves and freedmen of the Familia, and whether this occurred in general before or after manumission. It is important also to compare, if possible, the age of female slaves at marriage with that of male slaves and to estimate, if the evidence permits, the average differential in age between slave-born husband and wife.

In the strict sense of iustum matrimonium between partners with conubium, which alone was recognised as legally valid in Roman law with all the legal consequences (e.g. law of succession) that were involved therein, it is not possible to speak of slave marriage at all, but only of contubernium or concubinage. This applied when one or both parties were of slave status. But the terminology of legal marriage (e.g. ‘uxor’, ‘maritus’, ‘coniunx’, etc.) is so constantly used of contubernium in the inscriptions and even in the legal texts themselves that it is convenient to speak normally of slave marriage and to use such terms as ‘contubernium’ and ‘matrimonium’ only when the distinction is relevant to the argument.

The direct evidence for age at marriage in the Familia Caesaris is small and is derived from inscriptions mentioning both the age at death of one of the partners and the number of years of married life they enjoyed. The difference between the two figures represents the age at marriage.