I foresee ructions from this one...
The one set of customers who would be most interested in this sort of thing are the one group who would benefit least, namely those ethnic groupings who favour close-cousin marriages. Some of these societies have rates of close relative marriages over 75%, and this custom has persisted for at least a thousand years (there's a passage in the Koran referring to it, with the comment that it is common knowledge then that first cousin marriages produces defective children), so the question with these societies is not how much harm the practise causes, but how on earth they've not succumbed to rampant inbreeding and genetic disease.
The only answer here is that whilst the close cousin marriage rate is over 75%, the percentage of breeding adults who are the product of these close cousin marriages must be much, much lower. Several factors will feed into this; quite often highly inbred people/animals are so genetically defective that the infant mortality rate is high, fertility rates fairly low (not least because genetic idiots aren't favoured as spouses) and of course there must be a fairly high adultery rate leading to quite a few "non-paternity" offspring. In a field of morons, out-bred non-paternity kids are going to shine; any interest in why this kid doesn't look like its father will be buried in the relief at finally producing a kid with a normal IQ.
All this will combine to produce families where little Mo, the clever one out of a family of knuckledraggers isn't actually the fruit of his father's loins at all, but rather the milkman's (or similar), and whereas in times past an unusually clever child would be valued as a familial asset, nowadays the suspicious daddy would get the DNA testing kit out, find out he wasn't the father at all and get rid of the kid somehow. Quite what this is going to do to these ethnic societies I leave to your imagination...