The following table summarizes both the average percent DNA shared for different types of relationships, and the expected range of percent DNA shared. Notice that many relationships share the same average percent DNA, or their ranges overlap. If you and a relative were to share 17% of your DNA, for example, there would be some probability that the relative is your aunt, your niece, your grandmother, your grandchild, your half sister, or even your first cousin.
The relationship 23andMe presents is the most likely relationship, based on not only the amount of DNA, but also the pattern of DNA segments, your self-reported ages, and your relationships to other relatives you both have in common. But there is great diversity in the amount of DNA shared between any two individuals with a particular relationship.
To view your amount of shared DNA and compare it to this table, go to a relative's profile page and select "View DNA details" in the section titled "Your genetic relationship." To see the additional possible relationships for an individual in your Family Tree, click on the relative in your tree and select "See other possible relationships."
| Relationship | Average % DNA Shared | Range |
| Identical Twin | 100% | N/A |
| Parent / Child | 50% (but 47.5% for father-son relationships) | N/A |
| Full Sibling | 50% | 38% - 61% |
| Grandparent / Grandchild Aunt / Uncle Niece / Nephew Half Sibling |
25% | 17% - 34% |
| 1st Cousin Great-grandparent Great-grandchild Great-Uncle / Aunt Great Nephew / Niece |
12.5% | 4% - 23% |
| 1st Cousin once removed Half first cousin |
6.25% | 2% - 11.5% |
| 2nd Cousin | 3.13% | 2% - 6% |
| 2nd Cousin once removed Half second cousin |
1.5% | 0.6% - 2.5% |
| 3rd Cousin | 0.78% | 0% - 2.2% |
| 4th Cousin | 0.20% | 0% - 0.8% |
| 5th Cousin to Distant Cousin | 0.05% | Variable |
To learn more, visit the International Society of Genetic Genealogy website.