Note 27 — Chapter VI · : The Matter of Clothes. A Feudal Wedding.
Reading edition
How serious the problem of the "forbidden degrees" could be is shown by the case of the pious Louis VII of France, who put away his wife, the great heiress Eleanor of Aquitaine, because he was the fifth in descent from Hugh Capet, who had married a sister of the great-great-grandfather of Eleanor. Of course, the marriage had actually proved uncongenial before this point was raised.