Tuesday, January 19, 2010

Consanguinity – It’s All Relative

It’s called consanguinity or collateral relationships and includes all of our indirect blood relatives. Indirect relatives are those from whom we are not descended (parents, grandparents, etc.) or who are not descended from us (child, grandchild, etc.). This list includes aunts, uncles, cousins, nephews, and nieces. Today, we will focus on that ever present relationship – the cousin.

One of the things that I have noticed outside of the realm of genealogy is the great confusion on what constitutes a second cousin. I will have to admit, I used this terminology in error for the children of my first cousin, until I happened upon a consanguinity chart that was posted in the Sullivan County Courthouse in Claremont, New Hampshire.

I asked the clerk to copy the chart and she graciously obliged. It cleared up the matter of relationship once and for all. The year was 1988 and I had been working steadily on compiling my family data for over ten years, but still was confused on this issue as I had been calling people by the wrong relational title since childhood.

Talkin’ About My Generation

To understand it a little better, I have provided a custom consanguinity chart below and I’ll explain it. First, second, third, fourth, and so forth cousins all share the same distance in generations from a common ancestor as you do. If you have the same grandparents as me, then we are first cousins. If we share the same great-grandparents, we are second cousins. If my great-great grandfather was your great-great grandfather, then we are third cousins. As long as the relationship is of an equal distance to that ancestor, then we can refer to that person as our first, second, third, etc. cousin.

These cousins are in the same generation as us – or as I have it on the chart below the 0 generation. The term generation is used for a number of identifications such as the baby boom generation, generation X, the greatest generation, the Pepsi generation, and even in cultural anthropology to designate time with an average of 30 years. In genealogy, generation has nothing to do with age, when a person lived, or a span of years in this case – it is in reference to distance from the common ancestor.

For example, my oldest first cousin Fred (half first cousin to be exact) was my father’s contemporary. Being only four years younger than my dad, the two played together as children. This particular cousin was 38 years my senior and had children older than me. We grew up in different eras – he experienced the Great Depression and World War II, while I did not. He was born during Woodrow Wilson’s presidency, while I was born during Eisenhower’s first term. To my knowledge, I never met him – but if I had, we would have had nothing in common.

My father with his nephew Fred Allen circa 1923

Although experientially we held no commonality, we were the same generationally as we shared the same grandmother. He was her oldest grandchild, while I was the youngest and was born two years after her death. Because we were of equal distance from the same grandmother, we are genealogically from the same generation. His mother and my father were two of my grandmother’s six children – they were of the same generation but had a 17 year age difference.

In 1978, I had the opportunity to meet five or six of my second cousins for the first time. Our common ancestor was our great grandfather. Their grandfather and my grandfather were brothers. Since we are of equal distance and hence in the same generation, we are second cousins.

To calculate the relationship from a common ancestor, count the “greats” and add the number one to find the degree of consanguinity. For example, Pete and I share the same great-great grandfather. We are of equal distance in generations; therefore, if we count the greats as being two and add one, this gives us a relationship of 3rd cousins. Lorrie and I happen to share a 3rd great grandfather – we are fourth cousins. This even works with grandparents. No “greats,” so we assign the value of zero; 0 + 1 = 1 and the relationship would be that of a first cousin.

A Cousin Removed

But what about those cousins who are not equal distance from the same relative as us, but share a common ancestry? Earlier, I mentioned the children of my first cousin (two of which who are older than me). While I incorrectly identified these kinfolk as second cousins, they are actually my first cousins, once removed. Now, I am sure we all have a cousin that we would like to remove at times, but our feelings about that individual do not come into play in regard to terminology. The term removed is used to designate the difference in distance we have from a common ancestor.

For example, my cousin Kathy is my first cousin Joan’s daughter. Joan’s mother was my mother’s sister. Still following? Good. Our common ancestor would be my grandmother who was also Kathy’s great-grandmother. Since we are of an unequal distance from this ancestor, the relationship is removed. As my first cousin is her mother, this makes us first cousins, once removed. Kathy’s children and I are first cousins, twice removed and her grandchildren are my first cousins, thrice removed.

This also works backward up the chart. My mother’s first cousin Don was my first cousin, once removed as our common ancestor was his grandmother who was my great grandmother. Since Don was also Kathy’s grandmother’s first cousin, she was related to Don as a first cousin, twice removed. The removed is counted down from the closest equal generational distance.

You can figure this by counting the generational differences from our ancestor that has equal generational consanguinity with the person in question. For example, my great-grandfather's first cousin would be my first cousin plus three generations or thrice removed. My grandmother's second cousin would be my second cousin plus two generations or twice removed. My mother's third cousin would have a generational difference of one generation and would be my third cousin, once removed.

I realize that it sounds terribly difficult and confusing, but it is not. Getting in the practice of using the correct relational terminology will help you in understanding and correctly communicating relationships. Good luck.


  1. what if me and my boyfriend's great grandfathers were brothers? what are we?

  2. My great great grandmother is my boyfriends great great grandmother. What does that make us? Third cousins once removed?