The purpose of marriage in legal texts and in Christian contexts is to produce legitimate heirs. We see this in the Liber Constitutionum which states that if a husband or wife dies before they produced children, the surviving partner could not claim back any property or money that exchanged hands at the betrothal. This suggests that all marriages were expected to produce children and that this was its primary function. This is, in law and literature, its only official function, a function which is clearly defined from the biological process of simply having children (for men at least). Thus, that a married couple would have children is a truism rather taken for granted in modern scholarship on any historical period. Reproduction is viewed as a fundamental and unavoidable facet of being married and therefore perhaps not worthy of rigorous exploration. This means that the motivations for deciding to have children cited by the inhabitants of the post-Imperial Western world have rarely been thoroughly examined, though Ville Vuolanto's 2015 study offers an excellent first step in this direction. A significant reason for this lack of scholarship is the simple fact that there are no documented cases of married couples remaining voluntarily childless for any reason other than Christian chastity. In legal texts, married couples mentioned as being childless, for example in cases of the premature death of one partner, are usually presented as if they desired children but were frustrated.

There are two primary motivations for procreation offered by the sources: first there is the continuation of the family, often expressed as either the protection of the patrimony, preservation of the family name or as a fulfilment of the marriage contract; secondly, procreation was for the emotional fulfilment of the couple. The separation of these two motivations is for the most part artificial. Since it was such a distinct and powerful facet of Roman and post-Imperial society, the idea that ensuring the continuation of a family name and the protection of family estates could be hugely emotionally fulfilling in its own right should not be dismissed. Nonetheless, dialogues concerning the ‘joy’ of having a child or of parenting tend to be sharply differentiated from discussions in the surviving primary material which concern inheritance or familial continuity.