From the Roman Council of Alexander II, A.D. 1065

Canon IX. That no one lead a wife from his own consanguinity up to the seventh generation or as far as kinship could be known. This was first established by Nicholas II.

You often discern these two things joined as if one were the explanation of the other: up to the seventh generation, or as far as kinship or cognation can be known. We have already warned in another place (at A.D. 1059) that the latter phrase does not extend the prohibited degrees beyond the limit established by the former; this may now be declared by the doctrine of St. Peter Damian in the little work written expressly On the Degrees of Kinship. For in order to show that up to the seventh degree (to be computed in the ecclesiastical manner) marriages are not lawful (Epistle 1), he first supposes that among blood-relatives marriages are not lawful (concerning which matter there was no question); then he establishes that those are blood-relatives whom the divine and secular laws call blood-relatives, and that those of this sort certainly are those whom the same laws admit into inheritance and cannot repel. "Let those be questioned," he says, "who judge in tribunals, who determine the business of causes, who insist upon scrutinizing the decrees of laws: if nearer relatives are lacking, are agnates up to the seventh degree not admitted either into inheritance or into guardianship? But in the inheritance of one to which you are admitted by right of consanguinity, in what way may you obtain his marriage as if you were a stranger? To what purpose also is so laborious a figure depicted among the sacred canons, so that it is bounded not only above or below, but also on each side by six degrees, if the seventh generation, as they assert, is completed by three persons numbered on this side and four on that side? (These were certain wise men of Ravenna)." Peter's argument returns to this: he who is not a stranger to someone is a blood-relative; he who is called by right to someone's inheritance is not a stranger to him; but he who is distant even in the seventh degree is called: therefore, this one is a blood-relative; therefore.

The same man (chapter 2) declares it in another way, warning that a fitting boundary was prefixed by the holy doctors, namely, that as far as it is possible to find the names of successions, kinship also lasts no less. He says indeed that the figure of human succession is bounded according to the example of the human body by six degrees, above and below and in those who come from the side; nevertheless he adds: although, for the grace of more abundant caution, the seventh generation also has been consequently numbered with these. If you weigh these things, as we warn in passing, you will understand how you may compose the things which above we brought forward from Isidore and Gregory the Great. Gratian, however, explains it in another manner at C. 21, q. 2 and 3, causa XXXV; please consult him. Finally (chapter 4), after reciting the canon of the Council of Meaux, which we described above at A.D. 845, he proceeds thus: According to this edict, therefore, of the synodal sentence, to whom the right of inheritance belongs, there also belongs nearness of stock. For they would not, as it is said, succeed into inheritance unless they pertained to the propagation of cognation.