Larry, has done an excellent explanation. This is at the heart of phasing. I do suggest that people use either Excel 2007 or newer or the latest version of OpenOffice/LibreOffice to at least glance at the results of at least three closely related persons test results from the same company. Pay particular to matching segments. Warning OpenOffice/LibreOffice become excruciatingly slow with the number of rows involved. Excel is tolerable. --------------------------------------------------------------------------- Jim, If you have AG at a location and you have two matches one of whom has AA and the other has GG, you will ?match both, but they will not match each other. ?FF has no way to know which of your parents you inherited the A from and which you inherited the G from. Regards, Larry