From the Epistle of Alexander II, to the Clerics of Naples: How the Degrees of Consanguinity Are to Be Computed, A.D. 1061-73

He vehemently rebukes those who enumerate the generations proceeding on either side from two brothers in such a way that they declare the sons of the same to be the fourth generation with respect to each other, the grandsons the sixth, the great-grandsons the eighth. And thus they divide one degree of generation, which undoubtedly must be called one, and unskillfully contend to cut apart the progeny to be numbered.

Namely, he rejects the method of computing of Roman civil law, as to nuptials.