A lady I know was walking past her neighbor's house in a WV holler, and heard a comotion inside. Peeked in a window and brother was knocking the bottom of his sister. Close family, I guess. That kind of stuff plays Hell with the genetic equation if not known, assuming the union bears fruit, or maybe fruitcake.
I believe the saying is "Closer kin, deeper in".
This happens in stock all the time. Breeding two genetically close individuals generally goes one of two routes or a combo of the two:
1. The offspring has accentuated the shared strong points of the related individuals' genetics and has a good outcome......we call this line-breeding.
2. The offspring has accentuated the shared weak points of the related individuals' genetics and has a poor outcome......we call this inbreeding.
If the genetics of both sides of the breeding have no strong points to begin with it doesn't take a geneticist to figure out what the results going to be.
