OK, this would probably be a case where the couple should be sad that they have learned they should not have children. But they are not brother and sister as far as family relationships are concerned. The whole reaction to this strikes me as weird.
On the other hand, I dimly remember stories from colonial America about non-blood related adoptive siblings who grew up together getting married. Now that always seemed perverse to me.
I think the Biblical/moral point is that we’re supposed to leave and find the other. Inbreeding occurs when we want to stay home and make what we know serve every need rather than risking.
There is a sense in which this couple has ended up not going “out” as far as they thought. But that wasn’t intentional and the fact remains that they are from different families as far as law and covenant are concerned. I don’t see why anullment should be enforced.
In colonial families, would the adopted children be truly adopted, or would they be raised by guardians who were not legally their parents? that would make a difference.
I had the exact same thought, Mark. In fact, although their children would have a higher chance than usual of genetic abnormalities, statistically the odds would still be in their favor. In any case the marriage should not have been annulled.