Sibling
A sibling is a relative of your own generation line, and the word works both ways: you are their sibling too.
The route
Red line: from you (1 step up) and 1 step down. Gold: the shared ancestor.
How to count it
Siblings share parents. Each is one step up from the shared parents, so a and b are both 1. If only one parent is shared they are half-siblings.
Cousin counting is the standard genealogical convention. Different families and legal systems sometimes use looser words, so check the naming conventions guide if a relative uses a different term.
Facts at a glance
| Term | sibling |
|---|---|
| Reciprocal | sibling |
| By gender | Man: brother. Woman: sister. |
| Steps up (a, b) | 1, 1 |
| Civil-law degree | 2 |
| Canon-law degree | 1 |
| Average DNA shared (full) | 50% |
| Average DNA shared (half) | 25% |
Full and half
The figures above assume full relatives, who share a couple as common ancestors. If the link runs through just one person, because of a remarriage or a different other parent, the relationship is a half relationship. It is usually written half sibling, and the average shared DNA falls to 25%. See full and half relatives.
The DNA numbers are theoretical averages. Real amounts vary a lot from one pair to the next, especially for distant cousins, so read the DNA guide before comparing against a test.
Check your own relationship in the calculator, or see where this term sits on the chart.
Nearby terms
- Before: 8th great-grandchild
- After: nephew or niece
- All terms