Relationships

Blood relationships are determined by computing the shared ancestry of two individuals. Typically, people express such relationships using terms that reflect the most direct relationship. That is determined by counting the generations from each individual to the closest common ancestor; siblings share a parent, first cousins share a grandparent, etc.

In contrast, consanguinity usually refers to a calculation of shared ancestry that includes all common ancestors.

Most cultures and languages have special terms to describe close blood relationships such as mother, father, parent, child, sibling, aunt, uncle, niece, nephew, and cousin. Those relationships are well-understood and it is not necessary to actually count the generations to know the relationship. Terms in common use for more distant relationships are generally less precise. In English, people who share an ancestor more than two generations back may simply be called cousins or distant cousins. Many people, for example, could not express the precise relationship between the Subject and the Cousin's Child as shown in the chart below:

Here's how to calculate the relationship.

The closest common ancestor is the Grandparent of the Subject (two generations) who is also the great-grandparent of the Cousin's Child (three generations).

When the number of generations to the common ancestor is not the same for both the subject and the relative, the first part of the relationship term is determined by the lesser of the two distances to the common ancestor. In this case, that is two, and so the first part of the relationship is "First Cousin". The second part of the relationship term is determined by the difference between the two distances to the common ancestor. In this case, that is one (three minus two), and so the relationship term is First Cousin, Once Removed.

After reading the above, one might be tempted to call a niece or nephew a "sibling once removed", but I don't recommend it!

Please note that a descendant of your first cousin can never be a second cousin to you. The number of times removed increases with each generation. As shown below, a second cousin is related through one of your great grandparents.

The chart shows an interesting characteristic of relationship terms. Most of the terms for near relations are not reciprocal: mothers and fathers have daughters and sons, aunts and uncles have nieces and nephews. The most common reciprocal term is cousin: cousins have cousins. Note that "1st Cousin Once Removed" appears twice in the chart. The child of your 1st cousin and the child of your great aunt or uncle are both your first cousin once removed. Note that the number of generations difference is the same:

The relationship from a child of your great aunt or great uncle to you is the same as the relationship from you to a child of your 1st cousin.

You can use the chart below to calculate the relationship between two people.

  • Count the generations between the common ancestor and person 1. Use that number to find the proper column.
  • Then count the generations between the common ancestor and person 2. Use that number to find the proper row.

The relationship is shown at the intersection of the column and row.


0 1 2 3 4 5 6 7 8 9
0 Common Ancestor Son or Daughter Grandson or Daughter Great Grandson or Daughter 2nd Great Grandson or Daughter 3rd Great Grandson or Daughter 4th Great Grandson or Daughter 5th Great Grandson or Daughter 6th Great Grandson or Daughter 7th Great Grandson or Daughter
1 Son or Daughter Siblings Niece or Nephew Grand Nephew or Niece Great Grand Nephew or Niece 2nd Great Grand Nephew or Niece 3rd Great Grand Nephew or Niece 4th Great Grand Nephew or Niece 5th Great Grand Nephew or Niece 6th Great Grand Nephew or Niece
2 Grandson or Daughter Nephew or Niece First
Cousin
First Cousin Once Removed First Cousin Twice Removed First Cousin
3 Times Removed
First Cousin
4 Times Removed
First Cousin
5 Times Removed
First Cousin
6 Times Removed
First Cousin
7 Times Removed
3 Great Grandson or Daughter Grand Nephew or Niece First Cousin Once Removed Second
Cousin
Second Cousin Once Removed Second Cousin Twice Removed Second Cousin
3 Times Removed
Second Cousin
4 Times Removed
Second Cousin
5 Times Removed
Second Cousin
6 Times Removed
4 2nd Great Grandson or Daughter Great Grand Nephew or Niece First Cousin Twice Removed Second Cousin Once Removed Third
Cousin
Third Cousin Once Removed Third Cousin Twice Removed Third Cousin
3 Times Removed
Third Cousin
4 Times Removed
Third Cousin
5 Times Removed
5 3rd Great Grandson or Daughter 2nd Great Grand Nephew or Niece First Cousin
3 Times Removed
Second Cousin Twice Removed Third Cousin Once Removed Fourth
Cousin
Fourth Cousin Once Removed Fourth Cousin Twice Removed Fourth Cousin
3 Times Removed
Fourth Cousin
4 Times Removed
6 4th Great Grandson or Daughter 3rd Great Grand Nephew or Niece First Cousin
4 Times Removed
Second Cousin
3 Times Removed
Third Cousin Twice Removed Fourth Cousin Once Removed Fifth
Cousin
Fifth Cousin Once Removed Fifth Cousin Twice Removed Fifth Cousin
3 Times Removed
7 5th Great Grandson or Daughter 4th Great Grand Nephew or Niece First Cousin
5 Times Removed
Second Cousin
4 Times Removed
Third Cousin
3 Times Removed
Fourth Cousin Twice Removed Fifth Cousin Once Removed Sixth
Cousin
Sixth Cousin Once Removed Sixth Cousin Twice Removed
8 6th Great Grandson or Daughter 5th Great Grand Nephew or Niece First Cousin
6 Times Removed
Second Cousin
5 Times Removed
Third Cousin
4 Times Removed
Fourth Cousin
3 Times Removed
Fifth Cousin Twice Removed Sixth Cousin Once Removed Seventh
Cousin
Seventh Cousin Once Removed
9 7th Great Grandson or Daughter 6th Great Grand Nephew or Niece First Cousin
7 Times Removed
Second Cousin
6 Times Removed
Third Cousin
5 Times Removed
Fourth Cousin
4 Times Removed
Fifth Cousin
3 Times Removed
Sixth Cousin Twice Removed Seventh Cousin Once Removed Eighth
Cousin