Did you know you can enter your first name into Wolfram Alpha and it will guess your age, based on US birth statistics. So it's a shot in the dark with Dutch names.
It's completely off, haha, since I emigrated. But my grandfather did indeed come from Scheveningen, which lies inside that one hotspot. There are basically a handful of last names that up to a few generations ago were as good as unique to that fishing village, and Van der Zwan is one of them. I try not to think too much about the genetic implications of that fact.
(now I wonder how you knew that "Kees" is a Dutch name)
(now I wonder how you knew that "Kees" is a Dutch name)