On May 26, 2016, 23andMe.com announced a new DNA Relatives In Common With feature for users on its new platform. This is very exciting news because the new tool will help us figure out who's related to whom among our DNA matches. Of course there are some caveats. Please read the announcement by 23andMe's moderator in the site's new community forum as seen here:
Using our Relatives in Common feature, you will be able to see the current matches that you and a DNA Relative have in common, and whether you share an overlapping segment of DNA among all three of you.
Once you have selected a relative to compare with, you will be able to review a list of relatives that you have in common, as well as the percent DNA shared and the predicted relationship between each pair.
You will also be able to see whether you have any overlapping genomic region among you, the person you are comparing with, and the relative you have in common. If there is a region of any overlap among all three of you, then we say that you have “Shared DNA”. Clicking on the blue “Yes” or “No” under Shared DNA will take you to DNA View where you can see the segment data.
This is what happened when I chose "Shared DNA" and clicked on the blue "Yes" ... The chromosome browser (used for Family Inheritance: Advanced tool) opens up and shows where you match the chosen common relatives on the chromosomes. It also shows if there is overlapping segments between you and the two other relatives that you share DNA with in the same location (see chromosome #18); if I had chosen "No" then it would show the locations shared between me and two other relatives who don't match each other in the same location (but are still related to each other).
23andMe shows each pair of chromosomes on one display. Even though you share DNA along the same stretch along the chromosome pair, the actual DNA that matches may be different as one individual may match on one chromosome of the pair while the other matches on the sister chromosome. So, it’s possible that even if it appears that the three of you have Shared DNA, it may be that you match each profile on the same region but through different sides of your family.
We’re really excited about our Relatives in Common tool. We are rolling this out gradually, so users who are opted in to Open Sharing will be the first to access the feature. If you want to start using this today, you can opt in to Open Sharing here.
Let me know if you have any questions!"