Also hobbits, seem to like to marry within their family, but they must share more of the same names than actual blood. And besides brother-sister, what about
a la Oedipus the King? In that play, his children (coming from him and his mother) did not have birth defecs, they were only looked on as 'monsters' in a symbolic sense.
And I recall that not only Cleopatra and Ptolemey, but the entire line of Egyptian rulers bred within their immediate family, which kep their bloodline "pure."
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TOYOTA RACING HISTORY