While a surname itself may give us incomplete or misleading or, at best, only general information about the origin of a family, DNA-testing can give us concrete evidence for identifying and separating family lines.  mtDNA, Y-DNA and autosomal FamilyFinder dna tests can be helpful indicators of branching. The accessibility and affordability of family DNA testing is doubtless the greatest technical advance in the history of genealogical research because -- at long, long last -- we have a tool to break down those brick walls!