Terminology
Genealogical terminology can be confusing. I hope this short tutorial will clear things up.
Ancestors
Everyone has 2 parents, 4 grandparents, 8 great-grandparents, etc. After the first great, it's customary to abbreviate to 2g instead of great-great, then 3g, etc. For a positive integer N, your Ng-grandparents number 2N+2, counting multiplicity. Your Ng-grandparents are N + 2 generations back.
If A is an Ng-grandparent of B, then B is an Ng-grandchild of A,
The parents of your father (or mother) are called your paternal (maternal) grandparents. Other relatives are sometimes called paternal or maternal, depending on whether they are related to you through your father or mother. So, for example, you have 2 paternal g-grandmothers.
Some ancestors appear in your tree more than once. For example, if your parents were 1st cousins, they have a pair of grandparents in common, and they would both appear twice in your tree, as g-grandparents. That's why I say you have 8 g-grandparents, "counting multiplicity," but only 6 distinct ones. I won't keep reminding you.
An Ng-grandparent of your Mg-grandparent is your (M + N + 2)-g grandparent.
Charts and Trees
It is common to display or imagine extended family relationships in a chart, informally referred to as a family tree. An ancestry chart, a.k.a. pedigree chart, shows the direct ancestors of an individual, going back some number of generations. A descendant chart shows the descendants of an individual or couple, sometimes showing spouses of descendants, going forward in time, some number of generations.
The chart shown above is a generic ancestry chart, showing 3 generations of ancestry for an individual. His parental line runs along the upper edge, from himself to his father, father's father, father's father's father, etc. Since Y-chromosomes are inherited from father to son, they are all in the same Y-haplogroup. Also, in most cultures, surnames are inherited from the father, so the ancestors on the top edge generally all have the same surname. On the botton edge, are the mother, mother's mother, etc. Since mt-DNA is inherited from the mother, they all have the same mt-haplogroup. The surnames generally change, each generation.
The nodes are often filled in with birth, death, marriage, and other information, and sometimes thumbnail photos or family crests. There are many ways to display the same information.
If different nodes are regarded as distinct individuals, an ancestry or descendant chart shows a perfect binary tree, in graph theory. If nodes corresponding to the same individual are glued together, the graph becomes very tangled. It is still a directed acyclic graph, but no longer a tree, and is generally impossible to display in a planar chart. So it is customary to allow them to appear separately.
An Ahnentafel (German for "ancestor table") is a numbering system for listing a person's direct ancestors in a fixed sequence of ascent. It's useful for everyone to use the same system. The numbers can be used as labels in an ancestry chart. For the Ahnentafel-retentive!
Numbers
As N increases, 2N+2 increases exponentially. For N = 10, going back 12 generations, we have 212 = 4,096, and this is the number of 10g-grandparents you have. Good luck finding names and dates for all of them! With about 25 years per generation, they were born roughly 300 years before you. For N=20, going back 22 generations, or some 550 years, we have 222 = 4,194,304. If you find one of your 20g-grandparents, very little of your DNA came from them!
I have approximate birthdates for 56 of my 4,096 10g-grandparents, almost 1.4%. They range from 1646 to 1734, with median 1673, mean 1676.375, standard deviation 20.477, skewed toward the later dates. With 12 generations from 1676 to 1956, the generations average about 23.3 years.
Since your number of ancestors increases exponentially as you go back in time, it quickly exceeds the population of the region where they lived, so some of your ancestors appear in your tree many, many times. Also, any two people have a common ancestor, if you go far enough back. If fact, any branch of your tree must intersect with any branch of mine, although we might never know the identity of the Most Recent Common Ancestor (MRCA). If all or most of the ancestors of two people, are known to have lived in an area with only a few million people, say 300 years ago, it becomes very likely that they have a MRCA within 12 generations.
For example, Charlemagne lived from 747 to 814 AD, so he was born 1,209 years before me, about 48 generations. He had 10 known wives or concubines, and at least 18 children. Anyone with west European ancestry is very likely a descendant of Charlemagne. My 46g-grandparents number almost 282 trillion, and the population of northwestern Europe, where almost all of them lived, was at most a few million. If I could fill in my tree that far back, Charlemagne must appear as my 42g to 55g-grandfather, millions of times! The chance that he is not my ancestor at all is essentially zero. Similarly, anyone alive today, with English or Scottish ancestry, is undoubtedly a descendant of King Edward I, who was born in 1239, and had 17 known children.
If everyone has 2 children, the population remains constant, from one generation to the next. If everyone has more (or less) than 2 children, the population increases (resp., decreases) from one generation to the next.
If everyone has 4 children, the population doubles every generation. Since a descendant chart shows all children, with or without spouses, the generations displayed grow by a factor of 4 each step. You have 4 children, 16 grandchildren, and generally, your Ng-grandchildren number 4N+2. If larger families are common, growth is even faster. A descendant chart with more than 3 or 4 generations becomes difficult to display on one screen or sheet of paper.
Siblings and Half-Siblings
Two people who have the same parents are siblings. (Brother or sister to each other.)
Two people who have only one parent in common are half-siblings. (Half-brother or half-sister to each other.)
Cousins
Two people who have a pair of grandparents in common, but different parents, are called 1st cousins.
It's not uncommon for a pair of siblings to marry a pair of siblings, especially in a small community, where choices are limited. In that case, children of each couple would share all 4 grandparents, so they would be double 1st cousins.
It's not uncommon for a widow to marry a brother of her deceased husband, or a widower to marry a sister of his deceased wife. Children of the two marriages would be half-siblings, because they have a parent in common, but they would also be 1st cousins, because their other parents are siblings.
Two people who have a pair of g-grandparents A and B in common, but are not both descendants of the same child of A and B, are 2nd cousins. It's possible that you and I have grandparents in common, on one side of our trees, and also a pair of g-grandparents in common, on the other side, so we are both 1st and 2nd cousins.
More generally, two people who have a pair of Ng-grandparents A and B in common, but are not both descendants of the same child of A and B, are (N+1)th cousins. We are all distant cousins, in many ways, although we will never know the identities of all the common ancestors.
If A and B are Nth cousins, then A and any child of B are Nth cousins 1x removed. The terminology is symmetric: if A is the Nth cousin 1x removed of C, then C is a Nth cousin 1x removed of A.
If A and B are Nth cousins, then A and any grandchild of B are Nth cousins 2x removed. And so on.
If 2 people A and B have a common ancestor, then they are siblings or cousins. If A has Ng-grandparents, who are also Mg-grandparents of B, the terminology depends on M and N. If M = N, then A and B are (N+1)th cousins. If N < M, then A and B are (N+1)th cousins, (M - N)x removed.
For example, Joseph SMITH Jr (1805-1844), the Founder of Mormonism and the Latter Day Saint movement, was a 3g-grandson of Aaron 3 HUNTLEY and Mary Champion, my 7g-grandparents. So Joseph Jr and I are 4th cousins, 4x removed.
If two people have only one grandparent in common, or one g-grandparent, they they are half-1st-cousins, or half-2nd-cousins, etc.
The chart below shows relationships of one person, labeled "self," to descendants of one pair of their 3g-grandparents. Each row describes one generation, descended from the generation above. This assumes that everyone had only one spouse. Otherwise there might be some half-uncles/aunts or half-cousins.
Aunts and Uncles
A sister of your parent is your aunt. A brother of your parent is your uncle. A son of your sibling is your nephew. A daughter of your sibling is your niece.
I don't believe there is a gender-neutral term of a sibling of a parent. They're either an aunt or an uncle. Similarly, a child of your sibling is your niece or nephew.
You probably call your parents' parents your grandparents, not great-parents, and their parents are your great-grandparents, not great-great-parents. However, the usage is mixed when naming aunts and uncles.
A brother of your grandparent is your granduncle, sometimes called great uncle. The latter is technically incorrect, but is in common usage. We should understand common usage, but but practice correct usage.
It's prudent to regard "great" and "grand" as synonyms, and count the number of greats plus grands. That tells you which generation a relative is in.
A brother of your great-grandparent is your great-granduncle, sometimes incorrectly called great-great-uncle. Two greats or grands.
We usually call a grandparent's father a great-grandfather, or g-grandfather, and his father is a great-great-grandfather, or 2g-grandfather, and so on. So a brother of your 7g-grandparent is your 7g-granduncle, and a sister of your 4g-grandparent is your 4g-grandaunt.
If A is an Ng-granduncle/aunt of B, then B is an Ng-grandnephew/niece of A,
A half-brother of your 7g-grandparent is your half-7g-granduncle.
For example, Elisha BOYD, a famous general and hero of the War of 1812, said to be the richest man in Berkeley County, VA (now WV), was the youngest son of John BOYD and Sarah GRYFYTH, my 5g-grandparents. I'm not a direct descendant of Elisha, so he is my 4g-granduncle, and brother of my 4g-grandfather, John BOYD Jr.
Thanks to Julia Payne for finding some of my mistakes! If you notice any mistakes or omissions, please let me know. It's important to get these things right.
Last updated 17 Jan 2023 by William Haloupek. Contact haloupek at gmail dot com.