‘Genealogy and the medieval historian’ by Michael Maclagan from the paper presented at the 1978 English Genealogy Congress held at St Catherine College, Cambridge.
If you have any interest in pedigree collapse and that your ancestors may have been related by multiple descent lines, then you will find Michael Maclagan’s paper of interest. He stresses “the wide spread of family connections through the Middle Ages”.
He gives examples of marriages forbidden by canon law that took place either by a clandestine marriage or by papal dispensation. The marriage between relatives has continued since medieval ages as Michael admits to be a child of second cousins.