Godmode said:
I think people who perpetrate incest on others should be given the death penalty against the consent of their family.
This is a harsh opinion, however I understand your sentiment. As this is a terrible and disgusting act.
In the first place, having sexual desire for ones sibling is unnatural and shows signs of something being wrong with the individual.
Under normal circumstances, even if your sibling is the hottest babe on Earth, or the most desirable man, you wouldn't feel sexual attraction to them since they are your sibling.
Same goes for a cousin or anything like that.
For far cousins you've never met before and whom you have a distant relationship with, it can happen you'll feel some sort of desire since they seem more distant from you, but even then common sense has to be applied and it must be understood that seeking sex for pleasure from them is not right, as there are many people whom one does not share a blood relationship with that one can seek out instead.
Also, a thing for anyone to keep in mind, if a person would be bad to have children with, such as is the case with incest or race mixing or in cases where the person is toxic and very draining, any sex for pleasure is to be avoided as well.
One would only diminish themselves by making strong connections with such people.
Ave Zeus!