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Relationship Terms

revised 29 Mar 2006

Copyright © 1996–2013 by Stan Brown, Oak Road Systems

Summary: The English language has quite an array of relationship or kinship terms, which can baffle even native English speakers. What’s the difference between a second cousin and first cousin once removed, or stepsister and half sister, let alone ortho-cousin and cross-cousin? This page demystifies some common and uncommon terms, with diagrams.



Different languages have different terms for relationships, and even distinguish different relationships. For instance, Swedish calls your mother’s brother “morbror” and your father’s brother “farbror”, where Danish has “onkel” for both, and English has “uncle”. (In Latin they were “avunculus” and “patruus”.)

On the other hand, English makes some distinctions that other languages do not. Your daughter-in-law and your stepdaughter are both your “belle-fille” in French. And according to the Encyclopædia Britannica, Polynesian languages use the same words for male and female cousins as for brothers and sisters.

Even native English speakers can be confused by some of our relationship terms. A friend asked me to help him figure out what relation he was to his mother’s aunt’s great-grandson. After we had worked that out (see Example 2), he suggested others might be interested. What follows is an expanded and more general form of our discussion.

In English, three sets of terms seem to cause the most difficulty: cousin, in-law, and “half” or “step” relations. Just to make things messy, each of these terms can correctly be used for several different relationships.

Vocabulary: In discussing relationships, phrases like “brother or sister” and “son or daughter” come up again and again. Here are standard gender-neutral terms that I’ll use to shorten the following discussion:

The Basics

Before getting into “third cousin once removed”, it’s good to understand the common terms. Please have a look at the following table.

         H = W                
 |                     |      
B0(M)=Z0(F)            C0(F)  
 |                     |      
B1                     C1     
 |                     |      
B2                     C2     
 |                     |      
etc.                  etc.   

H and W (a husband and wife) are the common ancestors of this family. B0 and C0 are the son and daughter (children) of H and W, and H and W are the father and mother (parents) of B0 and C0. B1 and C1 are the grandchildren (grandsons and gradddaughters) of H and W, and H and W are therefore the grandparents (grandfather and grandmother) of B1 and C1.

Aunt, Uncle, Niece, Nephew

There are standard words for collateral relationships, where neither person is directly descended from the other. B0 and C0 are brother and sister, or more generically siblings. Going down one generation, on one side only, we have four common relationships:

Children of your aunt or uncle are your first cousins. More generally, B1 and C1, and all their descendants, are cousins to each other. A separate section below details all the words used to describe cousin relationships.


Many children have godparents chosen for them by their parents, for example in Christian denominations at the time of baptism. While the godparents are not necessarily relatives, in some families they stand in the position of relatives to the child, and may even be addressed as “aunt” and “uncle”.

The godparents, in turn, may speak of their godson or goddaughter, and collectively godsons and goddaughters would be godchildren.

Honorary Aunts and Uncles

In some sections of the country, it is common for children to call their parents’ friends “Aunt Flo” and “Uncle Ed”. Perhaps because I grew up with this, it has always seemed charming to me: more respectful than first-naming them, much warmer than “Mr. and Mrs. Hendricks”.

Terms Involving “Great”

The American Heritage Dictionary of the English Language (Third Edition, 1992) gives sixteen definitions of the adjective “great”. The one that concerns us here is

great adj. 15.  Being one generation removed from the relative specified. Often used in combination: a great-granddaughter.

Apply this definition to B2 and C2. They are one generation below B1 and C1, who are H and W’s grandchildren. Therefore B2 and C2 are H and W’s great-grandchildren. H and W in turn are the great-grandparents (great-grandfather and great-grandmother) of B2 and C2. If we drew the family tree another generation down, B3 and C3 would be the great-great-grandchildren of H and W, and so on.

The collateral relationships can be “great”, too. Since B0 and Z0 are the aunt and uncle of C1, they are the great-aunt and great-uncle of C2. That makes C2 their great-niece or great-nephew. (The American Heritage Dictionary of the English Language (Third Edition, 1992) says that the unhyphenated spellings “great aunt” etc. are equally acceptable, and lists grandaunt etc. as less common forms.)

Unfortunately, language is not logical: there are no great-cousins. Instead, the terminology is cousins so many times removed, as explained below.

Terms Involving “In-law”

There are several of these, but most give little difficulty to native speakers. Any relationship term ending with -in-law indicates that the relationship is by marriage and not by blood; in other words, one of us is a blood relative of the other’s spouse.

If I want to refer collectively to the blood relatives of my spouse, I can call them “my in-laws". Sometimes this term means just my spouse’s parents; other times it can mean any group of my spouse’s relatives.

In-law relationship terms are always written with hyphens, by the way. And the plural is formed on the part before the “-in-law”; for example, “brothers-in-law” and not “brother-in-laws”. The only exception is the general term “in-laws”, which is always plural.

Father-, Mother-, Son-, and Daughter-in-Law

My father-in-law is the father of my spouse; my mother-in-law is the mother of my spouse. If my own parents get divorced and remarry, their new spouses are my stepparents, not my mother-in-law and father-in-law.

The husband of my daughter is my son-in-law; the wife of my son is my daughter-in-law. If my spouse has children from a previous marriage, those are my stepchildren, not sons-in-law or daughters-in-law. I am their stepfather or stepmother, not their father-in-law or mother-in-law.

In these days of more fluid relationships, it is becoming more common to say “daughter-in-law” of the woman my son or daughter has lived with for a long time. On the one hand, that’s a nice way of recognizing long-term relationships that don’t involve a traditional marriage. On the other hand, it’s a bit confusing to use the term “in-LAW” for relationships that are not recognized by law.

Brother-in-Law, Sister-in-Law

These are the only really tricky in-law terms. “Brother-in-law” and “sister-in-law” each have two or three meanings. All authorities agree on the first two meanings, but there is some controversy about the third (and I personally don’t accept it).

My sister-in-law could be:

  1. the sister of my spouse, or
  2. the wife of my brother, or
  3. the wife of my spouse’s brother. (This meaning is accepted by The American Heritage Dictionary of the English Language (Third Edition, 1992), but not by all authorities.)

Similarly, my brother-in-law could be

  1. the brother of my spouse, or
  2. the husband of my sister, or
  3. the husband of my spouse’s sister. (This meaning is accepted by The American Heritage Dictionary of the English Language (Third Edition, 1992), but not by all authorities.)

Consider the following example: Al marries Betty; Betty has a sister Bonnie, who marries Calvin.

         Harry = Sally                
      |                  |            
Al = Betty            Bonnie = Calvin 

The siblings-in-law:

So much is agreed. The question is, are Al and Calvin brothers-in-law (definition 3)? Someone once wrote to Ann Landers, the advice columnist, describing this situation. Ann replied: “You are no relation; you are just two men who married sisters.” Though I agree with Ann on this one, I admit that it’s awkward for Al to refer to Calvin as “my wife’s brother-in-law” or “my sister-in-law’s husband”. Probably that’s why Al might refer to Calvin as “my brother-in-law”.

Terms Involving “Cousin”

Children of the same two parents are siblings, brothers and sisters. (If they have only one parent in common the relationship needs the modifier “half”; see below). Other relatives who are descended from a common ancestor are generally called cousins. This section explains more specific terms for various degrees of the cousin relationship.

Please refer to this family tree for the following discussion.

         H = W             
 |                     |   
 |                     |   
B1....first cousins....C1  
 |                     |   
B2...second cousins....C2  
 |                     |   
B3....third cousins....C3  
 |                     |   
B4...fourth cousins....C4  
 |                     |   
etc.                  etc.

H and W are the common ancestors (husband and wife); B0 and C0 are their children, B1 and C1 are their grandchildren, B2 and C2 are their great-grandchildren, and so on.

First Cousins, Second Cousins, and So On

B1 and C1 are called first cousins. Because their parents (B0 and C0) were siblings, they are the first generation below siblings. Another way to look at it is that B1 and C1 each have two pairs of grandparents, of which they share one pair (H and W). (First cousins are sometimes called cousins german, or simply “cousins”.)

Next consider B2 and C2. Their respective parents, B1 and C1, are first cousins. B2 and C2 are therefore second cousins: they are the second generation below the level of siblings. Each number in front of the word “cousin” corresponds to going another generation down both sides of the family tree.

These cousinly relations all assume that the generations trace back to (full) siblings (B0 and C0 in the diagram), who had both parents (H and W) in common. If B0 and C0 had only one parent in common, they are half siblings, and all the cousinly relations below them would be preceded with the word “half”, according to William Addams Reitwiesner’s article “First Cousin Second Cousin” in on 24 Jun 2000, archived here. Though the terms exist, they are not used very often in ordinary conversation about one’s own family.

Types of First Cousins

First cousins can be classified two ways: patrilateral or matrilateral, and cross- or ortho-cousins. While ortho-cousins are children of two brothers or two sisters; cross-cousins are children of a sister and brother. Someone is your patrilateral cousin if you are first cousins through your father (and your father’s brother or sister); someone is your matrilateral cousin if you are first cousins through your mother (and your mother’s brother or sister).

Note that these terms depend on the sexes of the parents, not of the cousins. A table and some examples should make the terms clear:

         Zebulon = Yetta            William = Virginia        
                 |                          |                 
 -------------------------------       -----------            
 |               |             |       |         |            
Abe = Beth    Cassie = Doug    Ed = Felicia   Georgina = Hank 
    |                |            |                    |      
   Jill             John         Jack                James    

Jack’s first cousins can be categorized as follows:

(This section was adapted from “Cousin Marriage” in the 1967 Encyclopædia Britannica.)

“Removed” Cousins

Now consider B1 and C2. What relation are they? C2 is the child of C1, and C1 and B1 are first cousins. Therefore B1 and C2 are called first cousins once removed, the most common example of a relationship designated removed.. The “once removed” means that one of the two relatives is one generation removed from being a first cousin with the other. Continuing, C3 is the grandchild of C1, who is B1‘s first cousin, so B1 and C3 are first cousins twice removed. Each “remove” corresponds to going another generation down one side of the family tree.

The word “removed” is used only when the relationship involves going down the family tree, to later generations. For instance, B2 and C4 are second cousins twice removed, not fourth cousins twice removed.

Example 1: What relation to you is Joe, your mother’s cousin’s great-grandson? Answer: In the chart above, the first cousins B1 and C1 must be your mother and her cousin. (If a relationship is just stated as “cousin”, usually that means “first cousin”.) You are then B2, the child of your mother. Your mother’s cousin is C1, and her great-grandson Joe would be C4, three generations below her. You (B2) are second cousin to C2; Joe is twice removed, or two generations below C2. Thus your mother’s [first] cousin’s great-grandson is your second cousin twice removed—and of course you are also his second cousin twice removed.

Example 2: A friend asked me to help him figure out what relationship he was to his mother’s aunt’s great-grandson. On the above chart, you’d place my friend at B2, his mother at B1, and her aunt at C0. Therefore the aunt’s great-grandson is at C3. My friend B2 and his relative C3 are second cousins once removed.

A Little Cousinly Algebra

For those among you who like algorithms, the idea is that in the phrase “Nth cousins R times removed”, you go up R generations in the longer branch to get to “Nth cousins”; then you go up N generations in both branches to get to siblings. Another way to look at it is that you go N generations up the short branch of the tree, cross over to a sibling, then go N+R generations down the long branch.

Terms Involving “Half” and “Step”

These terms apply when parents remarry. Sometimes they are used interchangeably, but they have distinct and well-defined meanings. The key distinction is that half siblings have one parent in common but not both; stepsiblings have no parents in common.

I’ll use the diagram below to illustrate these relationships. Mark and Sally had a son named John, and Harry and Sue had a daughter named Amanda. Mark and Sue died (or the marriages ended in divorce). Harry met Sally; they married, and had a daughter named Amelia.

Mark = (1) Sally (2) = (2) Harry (1) = Sue 
  (1958)          (1968)           (1957)  
     |               |               |     
     |               |               |     
     |               |               |     
  John            Amelia           Amanda  
(1960- )         (1970- )         (1961- ) 

Step Relations

When a parent remarries, the new spouse is the stepfather or stepmother of any children from the previous marriage. For instance, Harry is the father of Amanda and Amelia and stepfather of John; Sally is the mother of John and Amelia and stepmother of Amanda.

The children from a previous marriage are stepsons and stepdaughters (generically, stepchildren). John is Harry’s stepson and Amanda is Sally’s stepdaughter.

By the way, you are no relation to your stepparent’s previous spouse. John, who is Harry’s stepson, might refer to Sue as “my stepfather’s ex-wife”, or simply “my stepfather’s ex”. (If he was hoping for Christmas presents, he might call her “Mom”!)

You are my stepbrother or stepsister if we have no parents in common but our parents have married each other. There are two ways you could be my stepsister:

A similar rule gives the two ways for you to be my stepbrother.

In the diagram, John is Amanda’s stepbrother and Amanda is John’s stepsister. They have no parents in common, but John’s mother Sally is now married to Amanda’s father Harry. Amelia is not stepsister but half sister to both John and Amanda, because she shares one parent with each.

Half Relations

You are my half brother or half sister if we have one parent in common but not both. For instance, if my parents divorce or my father dies and my mother remarries, her new husband is my stepfather. If she and my stepfather have a daughter, that daughter is my half sister because we have the same mother but different fathers. The same is true if my father remarries and has a daughter with his new wife: that daughter is my half sister.

In the diagram, Amelia is John’s half sister and John is Amelia’s half brother, through their common mother Sally. Similarly, Amelia and Amanda are half sisters through their common father Harry.

Do you see the difference? If you are the child of my stepparent, you will be either my stepsibling or my half sibling. “Half” means you are the child of my parent and my stepparent; “step” means you are the child of my stepparent and someone else (not my parent). Half siblings have one parent in common; stepsiblings have no parents in common.

By the way, “stepbrother” and “stepsister” are always written as single words, without hyphens. “Half brother” and “half sister” are each written as two words (source: The American Heritage Dictionary of the English Language [Third Edition, 1992]). Isn’t English a strange language?

Consanguinity, or Degree of Kinship

Degrees of consanguinity are used to compare the closeness of relationships in a legal context. For instance, if a person dies without leaving a will, his estate will be divided according to a legally prescribed order. Also, incest taboos prevent people marrying who are too closely related.

Consanguinity can be lineal, where one person is an ancestor of the other, or collateral, where the two people have a common ancestor but neither one is an ancestor of the other. Computing lineal consanguinity is easy: how many generations of descent are there? Thus a father and son are related in the first degree, a grandfather and grandson in the second degree, and so on.

      H = W
 |           |
B0(M)        C0
 |           |
B1           C1(F)
 |           |
B2           C2
 |           |
etc.        etc

Collateral consanguinity is trickier, and in fact there are two main systems:

(The above draws somewhat on François Velde’s Usenet article “Degrees” in [28 Oct 2003, archived here], and the 1911 Britannica article Consanguinity. Recent editions of the Britannica go into computation of consanguinity on the basis of shared DNA. On that basis great-grandparent and great-grandchild are related in the same degree as first cousins, because statistically each relationship involves 1/8 shared DNA.)

Life Changes, Relationship Changes

The terms given above have a long tradition behind them, but they came into use when society was a lot less mobile than it is today. Professional genealogists do it with diagrams and symbols, but how do various life events change the terms the rest of us use for relationships?

Adoption: The rule here is simple: Unless you’re a member of a European ruling house, someone who’s adopted is every bit as much a relative as someone who was born into the family. Whether your sister adopts a little girl or gives birth to one, that little girl is your niece. Whether or not little Jennifer knows she was adopted, you are her Aunt Helen and she is your niece. You wouldn’t refer to her as your adoptive niece, implying she’s not your “real” niece.

What about parents? Most adoptions occur when the children are very young. Their adoptive parents are most likely the only ones they know, and are usually referred to as mother and father. The woman who actually gave birth to the child is called, logically enough, the birth mother.

Death: For instance, if your husband dies, are his sister’s children still your nieces and nephews? Almost everyone would agree that they are. They’re not going to stop calling you “Aunt Helen”, presumably.

Divorce: This is the trickiest area. If you and your husband divorce, obviously his mother is still their grandmother, but is she still your mother-in-law? Some people would say yes; some would say no. Judith Martin (in Miss Manners’ Guide to Excruciatingly Correct Behavior; Atheneum, 1982; pages 565–6) favors some creative ambiguity, especially in everyday speech. Particularly if you are on good terms with them, whatever your relationship with your ex-husband, there’s no reason you can’t continue to call his children your nieces and nephews or why they shouldn’t go on calling you Aunt Helen.

If you need to make the relationship clear, you can always use a few extra words. My ex-husband’s stepbrother” is much more precise and accurate than “my brother-in-law”, but if you and the latter are on good terms there’s nothing wrong with speaking of each other as brother- and sister-in-law. The one exception, of course, is that divorced spouses can no longer refer to each other as “husband” and “wife” but must use “ex-husband” and “ex-wife” (informally, just “ex”), no matter how amicable the divorce.

Remarriage: Here, as with divorce, there’s no hard and fast rule. Depending on the connection you feel with the people in question, you could describe them as “my nieces and nephews” or “my first husband’s nieces and nephews”.

Of course common sense comes into it too. “Wouldn’t it be rather sweet”, Miss Manners asks, “to hear one grown man refer to another as ‘the father of my children’?” Well, maybe; but “my wife’s first husband” is a lot more clear.

Index of Terms

adoptive niece aunt birth mother brother-in-law brother child children collateral relationships collateral consanguinity cousins german cousins cross-cousins daughter-in-law daughter father-in-law father first cousins once removed first cousins twice removed first cousins godchildren goddaughter godparents godson gradddaughters grandaunt grandchildren grandfather grandmother grandparents grandsons great-aunt great-cousins great-grandchildren great-grandfather great-grandmother great-grandparents great-great-grandchildren great-nephew great-niece great-uncle half brother half siblings half sister husband in-laws lineal matrilateral cousin mother-in-law mother nephew niece ortho-cousins parent patrilateral cousin removed second cousins sibling sister-in-law sister son-in-law son spouse stepbrother stepchildren stepdaughters stepfather stepmother stepsiblings stepsister stepsons uncle wife

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