Some countries, that allow residency by decent, do so based on only one or two generations of close direct ancestors (parent, grandparent possibly great grandparent) by providing historical record proof that one or more of them was/were
born in (and in some cases
died in) that country. That might be doable for your cousin if his own parents or grandparents were born in the eastern EU country.Doubtful if only his wife's relatives were.
However, it would be wrong for anyone looking at their Family Search map to use it to say that their
DNA ancestry/ethnicity is actually that region/country's. I know that you didn't say that. I'm just using your post as a stepping stone because I see too often that some others seem to assume they should
test as a DNA ethnicity because their ancestors lived in a certain region/country.
Family Search does not DNA test. So where these people that Family Search placed on a map are from, and from whom they descended, is based on what people have entered into a tree on Family Search. Those people may have used one or a combination of family knowledge, historical records and/or assumed or confirmed relationship to a DNA match from another site. If I am correct, it appears that the people who are placed in certain regions on the map that Family Search shows for
me, are people
I added as my relatives into my tree. I may have just copied someone's else's information. I may or may not have researched and added historical records to back up my research and if I did add records they can be wrong, as can I. I certainly didn't only add DNA matches. We can't rely on family trees to be factual. I can't look at
my Family Search map and say that because Family Search placed my great-great grandparent on Sweden that he was, and I am, genetically Swedish.
OK off my soap box. Thanks for the step up.