We can figure out how close two people are related to each other using the measurements units called centimorgans. The count of centimorgans that can be analyzed is estimated amount of shared DNA, which attribute to a recently shared ancestor.
To understand what kind of relationships like “half-aunt” and “third cousin once removed” mean, you can review AncestryDNA match categories.
Centimorgans as Units of Measurement
A centimorgan is a measurement unit that we use to analyze the probability of a DNA section that will pass on to a descendent intact (rather than spliting into individual segments). A single centimorgan denotes a one percent chance that a DNA section will divide into separate segments within a particular generation.
These centimorgans are not a measurement unit for physical distance, but rather it is a unit for probability. In general, only two people share the more centimorgans, those are most closely related to each other.
You can read more details about centimorgans: Here
- In the list of AncestryDNA matches, review the second column to check the number of centimorgans you share with each of your DNA matches. To know details about which relationships may be possible with that number of centimorgans shared, press on the “Information” icon appear next to the column of number of centimorgan.
- The shared centimorgan result information that will appear there, displays how likely various relationships are possible between you and those DNA matches.