To me it is a very easy problem to solve. Just as we have the option to chose Nature and Magic, the same option can be made for Marriage or Matching. And like Magic and Nature, there are limitions and conquenses of one's choice. Stop both men and women fom procreating at age 50, therefore the cases of parnet/child unions occuring are slim. Or just go back to the fromat of VV1; when the child is born, we have no idea (unless you record the family) who the parnets/siblings are.
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Life is hard. So put on your big girl panties and deal with it.