The Alexander DNA Project has in its DIRECT lineages two different different men who were members of two different families who had "life events" in Cumberland Co., PA:
Benjamin b. ca 1725 Cecil Co., MD, d. aft 28 April 1807; m. Susannah Polk, ca 1747, in Cumberland Co., or Bucks Co., PA. They lived in Germantown, PA, w. of Philadelphia, PA when they migrated to Mecklenburg Co., NC.
James Alexander, b 25 Sep 1770 in Guilford, Franklin Co., now Cumberland Co., PA, d 3 Oct 1821 Cincinnati, OH, buried Knox Co., IN, m 1793 Botetourt VA Mary Dean Rose, b 1766 VA, d 12 May 1841, buried in Knox Co., IN.
Geographical proximity we have learned in the DNA project is not a for-sure indicator of a relationship.
If you are interested in learning more about Alexander DNA lineages, results and testing, you can go to http://alexanderdna.org/http://alexanderdna.org/