Thank you to (MHGS) Midwest Historical and Genealogical Society’s favorite IT guy for this article: 23andMe Informed Me My Husband and I Are Related: https://www.thecut.com/2018/12/23andme-informed-me-my-husband-and-i-are-related.html.
When it comes to DNA, endogamy – https://isogg.org/wiki/Endogamy can play a part in making relationships appear closer than they turn out to be.
Endogamy is the practice of marrying within the same ethnic, cultural, social, religious or tribal group. In endogamous populations everyone will descend from the same small gene pool. People will be related to each other in a recent genealogical timeframe on multiple ancestral pathways and the same ancestors will, therefore, appear in many different places on their pedigree chart. Endogamy can be the result of a conscious decision or cultural pressure to marry within the selected group but also occurs as a result of geographical isolation (for example, in island communities).
I have some instances of endogamy in my family lines. My paternal grandparents were from a small isolated community in eastern North Carolina. On my maternal grandmother’s side, one of her groups were Acadian. My ex-wife was from a small Kansas town and she said she was related to everybody in town, half by blood and the other by marriage. It was a small enough town there may have been a handful of exceptions to her comment, but I believe overall her statement was accurate.