People whose ancestors live in small Dutch immigrant settlements have probably noticed that many of them were distant cousins. The size of these communities limited the pool of potential spouses. Endogamy (marrying within the community, also known as ‘kissing cousins’) is not unusual.
What most people don’t realize, is that many of these settlers came over as a group. Their community did not start across the ocean, but may well extend over several centuries. The places of origins were often small too, so the cousin marriages may have been going on for a lot longer than you might think.
One example is Winterswijk, a village in Winterswijk where most people today are cousins of mine one way or another. Read about the worst case of pedigree collapse I have ever encountered. Many people emigrated from Winterswijk in the 19th century and settled in small towns in western New York and Wisconsin, still marrying the same families.