Still wouldn't match the Hapsburgs in terms of physical degeneracy, they deliberately married to close relatives (usually uncle/niece) over 200 years and the last one was severely disabled, had to eat behind a curtain cos he couldn't keep all the food in his mouth, both his wives complained he was impotent - he finally died aged 39 with no offspring.
Geneticist looking at his family tree reckon he would have been more inbred than the offspring of a brother and sister.
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The longevity of Liz & Phil plus their sprogs suggest there's been some outbreeding somewhere.