Earlier today, I was trying to remember the correct terminology for kinship terms, as I wanted to respond to a Facebook post that my cousin made about her new niece. My cousin’s sister is obviously also my cousin but I wasn’t sure exactly what that would make the relationship between me and her daughter.
My guess/recollection was that we are (first) cousins once removed, and this turned out to be correct. While checking it (on Wikipedia, of course) I discovered a good mnemonic for remembering or calculating the degree of cousinship between two individuals. It only works in English, although it’s possible that similar tricks could be devised for some other languages.
All cousins, of any degree, have common ancestors once you go back enough generations. First cousins are the children of siblings (the cousins I was referring to earlier are the daughters of my mum’s brother). This means that they have at least one grandparent in common (the terminology gets even more confusing when you start to consider step-siblings etc., so I’ll ignore them for the rest of this post). Second cousins are the children of first cousins (e.g. if I ever have children they will be second cousins of my cousin’s daughter, i.e. of my cousin once removed) and hence have a great-grandparent in common, and so on.
First, second, third, …., nth cousins are at an equal distance from the closest common ancestor. For example, my grandmother is also the grandmother of my (first) cousin. If the distances are unequal, you get a “removed” relationship, with the number of the removal being the number of steps away from equality. My aforementioned cousin once removed is the daughter of my first cousin. Her great-grandmother is my grandmother. Going in the other direction, my parents’ first cousins are also my cousins once removed (their grandparents are my great-grandparents).
The degree of the relationship from which the removal is calculated is based on the nearer of the two distances to nearest common ancestor. My cousin’s father is also one step away from me in proximity to my grandmother (his mother) but he is my uncle (and I’m his nephew – these terms don’t have the same symmetry as the cousin relationships, at least in English) rather than my cousin once removed.
To make things even more confusing, the term ‘cousin’ on its own can refer specifically to first cousins or more generally to cousins of any degree, including removed ones, or even people who are not actually strictly related at all. Incidentally, I also figured it was easiest to refer to all relatives (including long-dead ones) in the present tense, since from a family tree point of view the relationships still stand (my great-grandfather is still my great-grandfather even though he died long before I was born).
The deliciously simple trick, as explained in the Wikipedia article on cousins (at least at the time of writing), is for working out the degree of “equal level” cousins. All you do is work out the closest common ancestor (e.g. great-grandmother) and then count the number of ‘g’s (in this example, it’s two – giving second cousins). For “unequal level” cousins, you start with the closer of the two distances to common ancestor (equivalent to the lower number of ‘g’s in the name) to get the degree, and then count the extra steps required on the other side to get the removal.
To return to the original example of me and my (first cousin’s daughter), our common ancestor is my grandmother and her great-grandmother (we also have a (great)-grandfather in common, but one is enough for the calculation); there is one ‘g’ in “grandmother”, so we’re looking at a first-cousin relationship; there’s one extra step of removal on her side, so she is my first cousin once removed (and as the terminology of cousin relationships is symmetrical, I’m her first cousin once removed too).
This post started out with the intention of being a short note, mostly for my own future reference, but seems to be turning into a full-scale treatise on the subject of kinship terms. Rather than go on any longer I’ll leave you to read the above-linked Wikipedia article on cousins if you want to know more about the subject (in particular, check out the groovy diamond-shaped Cannon Law Relationship Chart near the bottom of the page).