His profile at WikiTree says that he is the last up the tree that had a contemporary charter identifying him - with his ancestors only being documented centuries later, and thus should be suspect as legendary.
https://www.wikitree.com/wiki/Arkel-34
"The van-Arkel ancestors listed before Herbaren van der Lede (Ca.1120) are based on the history writers from the 1600s, such as Batavia Illustra (1685) and Leven der doorluchtige Heren van Arkel (1656). There is much doubt around these geneaologies, as they are probably more folklorisch and legendary. The origins of the van-Arkels is probably rooted in the Counts of Teisterbant."
