I am of course talking about consensual incest, and consensual incestuous relationships. One could argue that such relationships are no more wrong than a consensual homosexual relationship and no more preventable than homosexuality. As far as the issue of children from a male-female (M/F) incestuous relationship (since yes, there exists the possibility of homosexual incestuous relationships...), yes, genetically, children from a M/F incestuous relationship have a higher chance of being afflicted with recessive diseases than children from non-incestuous relationships. However, children from a M/F Sub-Saharan African relationship have a higher chance of being afflicted with sickle-cell disease than children from non-Sub-Saharan African relationships. Other examples could be found. Should these relationships then be banned as well on the grounds of genetic concerns? Overall, this enters a realm analogous to the abortion debate: at what objective point do you establish a line that can't be crossed? Then you have the issue of childless relationships, as SeVeR has indicated. With a childless relationship, all genetic concerns about children from said relationship would be rendered moot. Would we start regulating which couples can have children, and which couples can't?