There are many incestuous relationships in the Bible. It is best to concentrate on the stories where there is some moral judgement, positive or negative, of those relationships. Some instances are merely described and not commented on. But some of those occasions include some of the most highly revered figures of the Bible, who are said to be righteous and just, like the person of Lot, who fathered children with his own daughters. Others, such as Abraham and his half-sister, are actively rewarded by God for incest (in their case, rewarded with a child). God made incest necessary by creating just two humans to start off with (Adam and Eve), and later, by killing off all humans except Noah and his family (at which time, animal-kingdom incest was just as necessary). Inbreeding causes countless genetic problems in families, which get worse per occurrence and leave detectable dents in the genetic makeup of species. Yet, in our genetic record there are no signs of periods of intense incest in Humans resulting from Adam and Eve, nor are there such signs in animals nor humans resulting from inbreeding after Noah's Ark. After creation, and after the flood, incest was rife and necessary, as part of God's plan. So it can't be bad or immoral, and to condemn incest is the same as saying that God's plan is evil. Even if you take the story of Adam and Eve and Noah as myths, their moral teachings imply that incest is ok. Strangely, in quite a few other places in the Bible, incest is also condemned.