When copying data from this family tree, please include a reference to the origin: Rob van Koert, "Family tree Van Koert", database, Genealogy Online (https://www.genealogieonline.nl/stamboom-van-koert/I9729.php : accessed March 5, 2026), "William de Ferrers, 5e Earl van Derby (± 1193-1254)".
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Request permission to copy data or at least inform the author, chances are that the author gives permission, often the contact also leads to more exchange of data.
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