When families migrate from one area to another, it can be hard to determine if you have really located the same group of individuals. The difficulty is compounded if the last name and first names are relatively common. It's important to be certain that the "true" family has been located and that one has not mixed up families with similar names. Male cousins bearing the same first and last name are particularly easy to confuse.
The rest of this article can be viewed here and was one I wrote for Ancestry.com in 2007.
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