Family Tree Relationships Explained: Cousins, Great-Grandparents, and ‘Removed’

To work out a family relationship, find the closest ancestor both people share and count how many generations each person is below that ancestor. The smaller count determines the cousin number; the difference between the counts is the number of times removed. Direct ancestors use parent, grandparent, and great-grandparent terms instead.

Direct ancestors and descendants

Your parents are one generation above you. Grandparents are two; great-grandparents are three; great-great-grandparents are four. Each additional generation adds another “great.”

The same pattern works downward: child, grandchild, great-grandchild, great-great-grandchild.

If a person is your ancestor or descendant, they are not your cousin in ordinary genealogical terminology, even though you share ancestry.

Aunts, uncles, nieces, and nephews

Your parent’s sibling is your aunt or uncle. That person’s child is your first cousin. Your grandparent’s sibling is your great-aunt or great-uncle, sometimes called grand-aunt or grand-uncle. Your great-grandparent’s sibling is your great-great-aunt or great-great-uncle.

Your sibling’s child is your niece or nephew; their child is your great-niece or great-nephew.

Family and cultural usage varies, so record the exact lineage as well as the label.

First, second, and third cousins

Cousin number describes the shared ancestor:

• First cousins share grandparents.
• Second cousins share great-grandparents.
• Third cousins share great-great-grandparents.
• Fourth cousins share three-times-great-grandparents.

Another rule: if both people are the same number of generations below the shared ancestor, subtract one. Two generations below gives first cousins; three gives second cousins.

What “removed” means

Removed measures a generation difference, not emotional distance and not whether the relationship is through marriage.

Your first cousin’s child is your first cousin once removed. You and your cousin share grandparents; their child is one generation farther from those shared ancestors.

Your grandparent’s first cousin is also your first cousin twice removed: you are two generations farther down than your grandparent.

The calculation method

Suppose Alice and Ben share ancestors Thomas and Mary.

1. Count generations from Alice up to the shared ancestors.
2. Count generations from Ben up to them.
3. Take the smaller count and subtract one: that is the cousin number.
4. Subtract the two counts: that is the removal.

If Alice is three generations below and Ben is four:

• smaller count 3 minus 1 = second cousins;
• difference 1 = once removed;
• relationship: second cousins once removed.

A small relationship table

When the rows differ, add the generation difference as “removed.”

Half relationships

Half siblings share one parent rather than two. Half first cousins descend from half siblings and share one grandparent rather than a grandparent couple. Continue the same logic for half aunts, uncles, and cousins.

Do not infer “half” merely because only one shared ancestor is currently known; the other may be missing from the tree.

Double cousins

Double first cousins occur when two siblings from one family have children with two siblings from another family. Their children share both sets of grandparents, creating two first-cousin paths.

Pedigree collapse and endogamy can create several paths between the same people. Record each path rather than forcing one label to describe all genetic and social relationships.

Relationships by marriage

“In-law” usually describes a spouse’s close relatives or a sibling’s spouse: mother-in-law, brother-in-law, and so on. The spouse of a cousin may be called a cousin-in-law informally, but usage varies.

Step, adoptive, foster, guardian, donor-conceived, and chosen-family relationships deserve explicit roles. A family tree should represent the family’s real structure rather than assuming biology is the only meaningful connection.

Why DNA relationship estimates differ

Genealogical relationships describe a documented path. Autosomal DNA inheritance is random, so cousins of the same genealogical degree can share different amounts, and distant cousins may share no detectable segment. Multiple relationship paths can increase shared DNA.

Treat a DNA range as evidence to compare with documented trees, not as an exact relationship label by itself.

Avoid counting errors

• Start at the closest shared ancestor, not a famous distant one.
• Count generations, not people in the chain.
• Use the smaller count for cousin degree.
• Use the difference for removal.
• If one person is the ancestor of the other, use direct-line terms.
• Check for half or multiple paths.

A plain-language alternative

For readers who find “third cousin twice removed” opaque, add the path: “Martha is the great-granddaughter of your great-great-grandfather’s brother.” The formal label helps calculation; the lineage explains the family connection.

When documenting the relationship, cite the parent-child link at every generation. A correct calculation built on one unproved parent is still an unproved relationship.

Further reading

• FamilySearch: Family Tree help
• FamilySearch GEDCOM specifications