Degrees of consanguinity
Laws on inheritance, marriage, jury service and conflicts of interest often say "related within the third degree". Here is how that degree is counted, both ways.
First cousin
2 up + 2 down
the longer of the two lines
Civil law: count every step
Start at one person, climb to the common ancestor, climb back down to the other person, and count each step. The ancestor is not counted as a step on their own. Your parent is 1st degree, your sibling 2nd (up to your parent, down to your sibling), your aunt 3rd, your first cousin 4th. This is the Roman-law method used by most modern civil codes and by most US states.
Canon law: count the longer line
The older church method counts only the generations on the longer side. Siblings are 1st degree, first cousins 2nd, second cousins 3rd. The Catholic Church replaced it with the civil method in the 1983 Code of Canon Law, but it still appears in historical records and some older statutes, so genealogists meet it regularly.
Consanguinity chart for common relatives
| Relative | Civil degree | Canon degree |
|---|---|---|
| Parent | 1 | 1 |
| Sibling | 2 | 1 |
| Grandparent | 2 | 2 |
| Aunt or uncle | 3 | 2 |
| Niece or nephew | 3 | 2 |
| Great-grandparent | 3 | 3 |
| First cousin | 4 | 2 |
| Great-aunt or great-uncle | 4 | 3 |
| First cousin once removed | 5 | 3 |
| Second cousin | 6 | 3 |
| Second cousin once removed | 7 | 4 |
| Third cousin | 8 | 4 |
This is general information, not legal advice. Statutes define their own counting rule, so check the exact wording that applies to you.
Questions people ask
What is consanguinity?
Consanguinity means a blood relationship: two people who share at least one ancestor. Relatives by marriage are related by affinity instead.
What degree of relative is a first cousin?
Fourth degree under the civil-law method (two steps up to the grandparents, two down), and second degree under the canon-law method.
Which method do US courts use?
Most US states use the civil-law method for inheritance and conflict-of-interest rules, but always check the specific statute, because some older rules and religious law use the canon method.