Furthermore, if you MUST inbreed, do not do it more than two or three generations max. Otherwise you start to mutate and have extra toes and fingers like the amish populations who don't get much new genetic material in their pools.

Did you know that in bees they use inbreeding to remove negative DNA, as the males only carry one set of DNA so any negative mutations or genes they may carry will be immediately evident and prevent their breeding.

So, in summation, if you want to not feel weird about it I wouldn't go any further than mutual oral/masturbation acts. Because if your parents catch you or anyone else you are never going to live that down. I'm sure the taboo wrongness would be exciting but I'm fairly confident the risks would make it simply not worth it.