One of the main reasons to perform a DNA test is to confirm and find long lost relatives, whether you knew they existed or not. According to 23andme, their “ability to detect first cousin relationships or closer is approximately 100%.” The following are the types of relationships and the approximate predication rates:
- 100%: identical twin
- 50%: father, mother, son daughter, brother, sister
- 25%: half-bro/sis, grandpa/ma, grandson/daughter, uncle, aunt, nephew niece
- 12.5%: 1st cousin, great-grandpa/ma, great-grandson/daughter, great-uncle/aunt, great-nephew/niece
- 3.125%: second cousin – same great-grandparents
- 0.781%: third cousin – great-great-grandparents
- 0.195%: fourth cousin – great-great-great-grandparents
- 0.05%: fifth cousin – gggggrandparents
- 0.0122%: sixth cousin – ggggggrandparents
Finding genetic relatives link here
| Cousin relationship | Probability of detecting |
| 1st Cousin or closer | ~100% |
| 2nd Cousin | >99% |
| 3rd Cousin | ~90% |
| 4th Cousin | ~45% |
| 5th Cousin | ~15% |
| 6th Cousin and beyond | <5% |
Percent DNA Shared by Relationship link here
| Relationship | Average % DNA Shared | Range [1] |
| Identical Twin | 100% | N/A |
| Parent / Child Full Sibling |
50% | Varies by specific relationship |
| Grandparent / Grandchild Aunt / Uncle Niece / Nephew Half Sibling |
25% | Varies by specific relationship |
| 1st Cousin | 12.5% | 7.31% – 13.8% |
| 1st Cousin once removed | 6.25% | 3.3% – 8.51% |
| 2nd Cousin | 3.13% | 2.85% – 5.04% |
| 2nd Cousin once removed | 1.5% | 0.57% – 2.54% |
| 3rd Cousin | 0.78% | 0.3% – 2.0% |
| 4th Cousin | 0.20% | 0.07% – 0.5% |
| 5th Cousin | 0.05% | Variable |
| 6th Cousin | 0.01% | Variable |
Once removed means a generation difference, and twice removed is a two-generation difference:
- Peter is my mother’s first cousin, who is my first cousin, once removed. It emphases on the relationship between Peter to my mom.
- Jane is your grandfather’s first cousin, she is my first cousins, twice removed.
