I have a few matches where I can't say for sure that we have uncovered the common ancestor, but we seem to have good leads. One is the surname Rockefeller. Henry Oscar Rockefeller compiled a family genealogy in the early 1900s, focusing mainly on this line, the immigrant Diell Rockefeller (died New York 1769), but also discussed some of the other Rockefeller lines in the area. I descend from Diell Rockefeller through my father's mother. At 23andMe, we both match a man who is descended from another immigrant, Johann Peter Rockefeller (died New Jersey about 1766).
Autosomal DNA comparison of the descendant ("Distant Cousin") of Johann Peter Rockefeller to my father and me.
We match on a small segment of Chromosome 12.
It is not known if Johann Peter and Diell were related. Does the above DNA comparison show that the two Rockefeller immigrants Johann Peter and Diell were related? Not necessarily. We could have other ancestors in common that we do not know about that are causing the match.
The DNA testing that could show if both Rockefeller immigrants were related is Y-DNA testing. Direct male descendants of both men could compare their Y chromosomes. The Y chromosome is passed almost unchanged from father to son and then to his son as so on down the line of descent. Neither my father nor our "Distant Cousin" here can participate in such a test because the last Rockefeller in both of their lines was a female, hence breaking the Y chromosome inheritance.