S.D. Codified Laws § 23A-20-30
The degree of kindred is established by the number of generations, and each generation is called a degree. The series of degrees form the line; the series of degrees between persons who descend from one another is called direct or lineal consanguinity; and the series of degrees between persons who do not descend from one another, but spring from a common ancestor, is called the collateral line or collateral consanguinity.
The direct line is divided into a direct line descending and a direct line ascending. The first is that which connects the ancestor with those who descend from that ancestor. The second is that which connects a person with those from whom that person descends. In the direct line there are as many degrees as there are generations. Thus the son is, with regard to the father, in the first degree; the grandson in the second; and vice versa with regard to the father and grandfather toward the sons and grandsons.
In the collateral line the degrees are counted by generations from one of the relations up to the common ancestor, and from the common ancestor to the other relations. In such computation the person whose consanguinity or affinity is being determined is excluded, the relative included, and the ancestor counted but once. Thus brothers are related in the second degree, uncle and nephew in the third degree, cousins germane in the fourth degree, and so on.
SDCL 23A-20-30