Re: The west
Glad that you googled it and ended up finding this defination 
well the standard that you have used to check whether a relationship is incestious or not, is certainly not correct.. The defination of incest lies in a question and that is “why is incest considered forbidden ?” Simply because it creates genetic problems in coming generations. Is not it so ? I still remember reading a medical report which says that the chances of catching genetic problems are comparatively low in case of cousin marriages as compared to direct blood relatives ( mother father sister brother and siblings of mother and father ) and problems come only when cousins marry each other generations after generations within a family. Well that says a lot.
I have another defination of incest too which is “spoiling the relation” but since you only understand the language of science, let’s not go there .