This is the first study to use pedigrees of a mainstream English population to determine cousin marriage rates amongst ordinary labourers, tradesmen and farmers, and to demonstrate the association between cousin marriage, occupation, religious affiliation, geographical mobility and illegitimate reproductive experience. Using birthplace rather than place of residence, it shows the geographical source of spouses, their parents and grandparents. The marriage prospects of parents of illegitimate children and the children themselves are described, along with the association between being the mother of an illegitimate child and both low geographical mobility and high rates of cousin marriage.