DNA matching has become a very important tool in genealogical research. The unit of measure is the centimorgan (cM.) The more centimorgans you match the closer related you are. It is not that simple. You also have to consider how many different segments you match and if the locations are the same. The length of the matching segments is also a critical issue. Most Ashkenazi Jews share a small amount of DNA due to the fact that they married within their communities. It wasn’t unusual for two first cousins to marry each other. DNA matching coupled with documented relationships can certainly establish that a connection is valid. Sometimes there are no documents to peruse but the DNA evidence is so strong that it must be so. I was recently able to decree that Beny Levin of Ft. Worth, Texas is my third cousin. I actually have addressed this relationship in earlier posts but I finally uncovered some additional DNA evidence that led me to this conclusion. Ancestry.co