The Roman calculated kinship only to the fourth degree. In the eighth cenury the Church extended the Roman system to seven degrees, as follow:

Self

1. Father and Mother
2. Brother and Sister, Grandfather and Grandmother
3. Uncle and Aunt
4. First Cousin
5. Second Cousin
6. Third Cousin
7. Fourth Cousin

In the ninth century the Church adopted the Germanic system of determining kinship:

Self

1. Father and Mother, Brother and Sister, Uncle and Aunt
2. Grandfather and Grandmother, First Cousin
3. Second Cousin
4. Third Cousin
5. Fourth Cousin
6. Fifth Cousin
7. Sixth Cousin