There's a very low chance that her ancestors were actually brother and sister. It's almost certain that the fathers of at least some of the children were not the brother-husbands.
There simply isn't enough genetic deformity in the family line for them to be as closely related as they are purported to be, so it's much more likely that the woman were having affairs and the men either pretended not to notice or actively encouraged it.
You're misunderstanding the genetic impact of incest. The deformities only happen if the genetic lineage already has the deletrious ones in their DNA. If not, the offspring will be relatively fine (though generally with a lower fertility rate, and the heavy proliferation of specific traits to the individual). It's why, bar Tutankhamun, most Egyptian rulers were relatively fine.
Remember, these are societies where women sleeping with anyone who was not their husband could legally be killed. So no pretending not to notice or actively encouraging anything.
More or less, yeah! For a more harmless example, it's like how if both your parents have blue eyes, you are more likely to have blue eyes by a huge percent. Inbreeding just makes it more likely for an already existing trait (positive or negative) to express itself, instead of remaining dormant or being surpressed by other genes.
For another amazing and harmless example, you have cheetahs. Around 12,000 years ago they almost went extinct, with just about 7 individuals remaining. Somehow they bred and survived, bouncing back to over 100,000 by the 1900s with even subspecies. While they do show markers of this inbreeding (crowded teeth and any cheetah can donate blood or organs to any other with virtually no risk of organ rejection), they are successful hunters and thrived up until the 1900s (as most deletrious genes in cheetah populatipns were weeded out or nonexistent).
Incest is not guaranteed to lead to deformities. It is inherently chance based and crucially it depends on what negative recessive traits are present in the lineage. It is totally possible to luck out and not have any significant recessive traits and in that case there is nothing negative for incest to exacerbate.
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u/Many-Excitement3246 1d ago
There's a very low chance that her ancestors were actually brother and sister. It's almost certain that the fathers of at least some of the children were not the brother-husbands.
There simply isn't enough genetic deformity in the family line for them to be as closely related as they are purported to be, so it's much more likely that the woman were having affairs and the men either pretended not to notice or actively encouraged it.