In both Philadelphia and London, the greatest cause for sanctions was marriage delinquency. For London, a unique source on Quaker marriages exists: the Quaker Family History Society has compiled a database of all London Quaker marriages from the meetings’ records. This allows a detailed examination of how the Society's mid-eighteenth-century reform efforts influenced metropolitan Friends’ marriage patterns, as well as monthly meetings’ prosecution of marriage offences.

Quaker marriage was distinctive in several ways. First of all, the Society held a doctrine of religious marital endogamy. Both George Fox and Robert Barclay argued that marriage to non-Quakers would have a negative spiritual impact on Friends. At least in theory, therefore, seventeenth-and eighteenthcentury Friends were allowed to marry co-religionists only. As Quakers rejected church weddings as part of their doctrine against professional clergy, the Society required Friends to marry in its monthly meetings. A marriage by a priest or a magistrate was considered irregular and might lead to reprimands by the Society.

While in Pennsylvania Quaker marriages were considered legal from day one, in England the law did not formally recognize them until the Marriage Act of 1836. However, they were ‘repeatedly held valid in the courts (when, for instance, the legitimacy of children was questioned)’. This was important not only for inheritance, but also as illegitimate children were excluded from important aspects of civil life, such as joining livery companies or claiming urban citizenship. A series of court cases during the early decades of the movement were decided in favour of Quaker marriages. These included cases of inheritance. In 1658 a Lincoln man argued his deceased brother's Quaker wedding was invalid, making the deceased's child illegitimate and therefore unable to inherit. Instead, the surviving brother himself ought to be considered the heir. The court decided against him. A manor lord in Carlisle in 1681 tried to end the tenancy of a Quaker widow and her daughter of their deceased husband and father's land, arguing that the child was illegitimate and could not inherit. This too was overturned by the court. In 1679, the Meeting of Sufferings consulted the attorney Thomas Corbett of Grey's Inn on the matter. He argued that marriages, though in catholic tradition understood to require presence of a priest for validity, in fact only required the mutual consent of both parties.