Board Thread:Theories and Speculation/@comment-26381547-20150509000749/@comment-5936871-20150509215635

@Bambusek Technically they could, it's only multiple generations of incest that cause birth defects so I'm sure the first two or three generations would be fine. But it's an Anime, so maybe that logic was disregarded altogether and in Naruto's World incest doesn't seem too uncommon.

@GreatestSin I agree with you that it's mostly from your POV, and I also agree with you that the Obito and Kakashi thing was an asspull. But I honestly don't think the Tenseigan thing is that big of deal.