This sort of generality is really premature and excessively restricts potential familial fornicatory prospects when in real world practice it doesn't need to be. For instance, if'n the first cousin you form a fornicative union with is like a fourth or fifth cousin, then yur're golden. You ain't got a worry bout nuttin. Hell, a third cousin won't do much except make the progenies eyes a little closer together, maybe a few webbed fingers or toes, but that's the worst it could get. Second cousins...now yur're getting into the grey area and messin with fire. Take it a step further and you can bet your bottom dollar that if by some chance your first cousin is a first cousin, then you definitely have to wrap it. It's basically codified in most families who practice the ancient biblical ways of Adam and Eve. I've seen a few people make that mistake and their progeny almost always came out a two header. Them things is just damn hard to kill and can be quite large with multiple extremities and quick as lightning. In ancient times it was these big boogers that all those mythologies talking about Titans came from (half God half man). Adam and Eve's children really can't be faulted. They had no choice in the matter. But we in modern times now. Follow these rules and you should be able to get a good crop of relatively normal lookin progeny that won't cause you no shame.