the reason it was not acceptable is because it was noted that when family members married & had children if there were any problems in the blood line like cancer , sickle cell , thyroid , etc. that the outlook for any children born of a union between  close relatives doubled & tripled  the chance of the children having the problems. Â
@WJo: Oh, I understand the reasons why it's not a good idea. I was just wondering why so many states still allow it. I know two married couples that are first cousins. One couple has no children. The other does. Their kids seem OK, but their grandchildren have genetic problems.
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