Thinking about bloodlines and the connection to inbreeding, I'm wondering if there is a reason/benefit for inbreeding in the elite families beyond consolidation of power or geographic isolation?
"Inbreeding and the Goldilocks Zone"
"just the right amount of genetic overlap"
For his part, Dr. Stefansson suggested what we might call a Goldilocks Zone for inbreeding. That term, which we usually see applied to exoplanets, refers to the idea that planets need to neither too far away from nor too close to their star in order to be able to support life. In much the same way, third cousins might actually have "'just the right amount of genetic overlap"', neither too similar nor too dissimilar, and so they enjoy a "'reproductive advantage"'. However, the underlying genetics of that explanation remain unknown.
Ultimately, Stefansson concluded that maybe our taboos against consanguinity, or the marriage of related people, haven't just overestimated existing risks - they've actually covered up potential "'benefits"':
"The take-home message is that …we, as a society of [the] 21st century, have basically ruled against the marriages of closely related couples…But in spite of the fact that bringing together two alleles of a recessive trait may be bad, there is clearly some biological wisdom in the union of relatively closely related people."
Charles II represents the extremest of examples, a sort of worse case scenario for inbreeding. And yet he - or at least a hypothetical person very much like him - remains a sort of benchmark for how people imagine the results of inbred relationships, when the most likely result of even first cousins inbreeding is a more or less healthy child. This taboo hasn't always been so strong.
In fact, two of the top candidates for greatest scientist of all time married their cousins. "'Albert Einstein"''s wife, whose maiden name was in fact Elsa Einstein, was a first cousin through Albert's mother and a second cousin through his father. And, as we previously discussed, "'Charles Darwin"' married his first cousin Emma Wedgwood, and in fact their mutual grandparents, Sarah and Josiah Wedgwood, were themselves cousins. (To be fair, after three of Darwin's ten children died young, he and his son George conducted studies into whether the family's long tradition of inbreeding had reduced his reproductive fitness. They ultimately decided this wasn't the case, on the rather strange grounds that "the widely different habits of life of men and women in civilized nations, especially among the upper classes, would tend to counterbalance any evil from marriages between healthy and somewhat closely related persons)…
The list also includes luminaries like "'H.G. Wells"', "'Igor Stravinsky"', "'Edgar Allan Poe"'…, film director "'David Lean"', Morse code inventor "'Samuel Morse"', Nazi-turned-NASA rocket scientist "'Wernher von Braun"', and even noted criminals "'Jesse James"' and "'Carlo Gambino"', not to mention a huge fraction of "'monarchs"' throughout history. And that's just people "who married their first cousins - the list gets even longer if we consider more distant relations…
https://io9.gizmodo.com/5863666/why-inbreeding-really-isnt-as-bad-as-you-think-it-is