>>96095097Second generation incest is where most problems come from.
Basically, since you get two sets of genes from your parents, your body uses one from each parent. If one does not chemically function, the other gene is used instead. The problem with inbreeding is that your genes are so similar that if this situation happens, there's no backup gene to fall back on.
So, as a result, the odds of getting the same gene as the parent is very high. If you have no flaws in your genes, feel free to impregnate your mother or sister all you'd like. But with modern humans, there is no such thing. Yet having a single or few bad genes completely obliterate a viable child isn't likely from an F1. F2 onward is where the actual issues would crop up.
So Nicole is probably a-okay to fertilize herself with her own son's sperm. But if they have a daughter together and Gumball wants to breed with his own daughter-sister? Well, maybe you should stop cat sinning.