I’m looking into consanguinity and the catholic church. This institution of cousin marriages is quite an impediment to modern societies. Both for cultural and socio-biological reasons because it leads towards clannish behavior. The church managed to break this up. Secular authorities also helped to break this form of inbreeding down. It seems both the church and secular powers did it because they wanted to charge fee’s for exemptions and also to weaken tribal loyalty among the barbarians. In the case of Aquinas and St. Augustine they believed it would make for a more christian society to interact in love people outside their kin.
I know this might be too specific an issue but do you know of any other religious or secular figures outside of St. Augustine and Aquinas who opposed cousin marriages? Or perhaps you know some sources or people I can consult?