Depending upon migration patterns, analyzing shared matches you have with a DNA match (especially one without a tree) may only add to your confusion.

A new match on AncestryDNA descends from a sister to my great-grandmother Tjode (Goldenstein) Habben. I clicked on our shared matches only to be reminded that when your family lived in the same area for generations (and migrated to that area from pretty much the same place as their immediate neighbors did) that shared matches may have nothing to do with your biological connection to that match.

This new cousin:

• was also related to my first cousin once removed (who is not a Goldenstein descendant). This is because this first cousin once removed’s mother (my aunt by marriage) and my new AncestryDNA match’s grandfather (not my relative) were brother and sister.
• was also related to a fourth cousin (who is not a Goldenstein descendant). This fourth cousin (on another side of the family) and my new AncestryDNA  cousin share a connection to the Weerts family in Adams County, Illinois–one that I do not share.
• was related to another fourth cousin (not a Goldenstein descendant). This fourth cousin and my new DNA match share a Golden, Illinois, family with each other that they do not share with me.

My new DNA match and I currently have 31 shared matches. Three of them are not Goldenstein descendants but share ancestral heritage with me that is separate from the ancestral heritage they share with my DNA match. My sample is anecdotal, but reminds me that when a relative and I share a larger cultural/ethnic heritage analyzing our matches might not be as easy as I would like.