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The Cousin Conundrum

I work with complicated topics in my research projects that can be difficult to explain. Haplogroups, shared centimorgans (cM) and X-chromosome matches will make your eyes glass over and your brain take a nap. While these cause confusion, the most frequently asked question I hear is what is a "removed cousin?" It never fails. I might be explaining a tree like the one shown below and the client who is "me" asks, how am I related to xxx, and then quickly followed by, "what does that mean?" When we talk about a "removed" cousin, it means the number of generations away from the relationship in our direct line to a target individual. This is my attempt to try and explain the cousin conundrum. Hopefully you can apply it to your family tree!

Summary of the Solution Steps

We will go through each one of these several times but here is the high level way to solve the riddle of "How are we related again?"

  • First, identify the common ancestor between the individuals in question.(MRCA = Most Recent Common Ancestor.) Without that information, you can't figure anything out. Start with zero (0) for the generation level of the common ancestor, number the generations all the way down to you as you draw out the tree.

  • Second, determine if you and the other person are on the same generational level or straight across from each other on the tree.

  • If you are on different generation levels, what is the target person's relationship to your ancestor directly across the tree from them? How many generations are you up or down from that matching ancestor? The equation is the type of the relationship with your ancestor, and the number of generations you are "removed" from that person. (2nd cousins, twice removed (2C2R) etc.)

Imagine this is your family tree below and not mine. Your GGG Grandfather at the top of the tree is generation #0 and is the common ancestor between you and who you are trying to figure out. On the far right of the picture is the generation number. His two sons are generation #1 and are full siblings. (Please contact me directly to discuss "half" anything!)

My Family Tree

Going forward in time, these two sons have descendants all the way down to my father, "R.G. Tonseth" and then me as the 5th generation. I am the descendant of Ole C.S. Tonseth and we will use Ernst A. Tonseth, Jr. and his descendants as the "target" individuals. I have drawn different colored lines to show the connections and the relationships, and explain them in the cousin table below.

Cousin Table

Same Distance from the Common Ancestor (Zero Removed)

If you are siblings or 1st/2nd/3rd cousins, etc., to someone, you are both at the same generation level and straight across the family tree from each other. It doesn't matter how far away from the common ancestor you are, if you are both at the same generation level you are cousins, without any "removal." If you subtract 1 from the generation level, that is your cousin designation. Example: Those who are at the 3rd generation level are 2nd cousins, if you are at the 4th level you are 3rd cousins, etc.

One Generation Apart (Once Removed or 1R)

Now starts the trickier part to being cousins. If you and the individual you are comparing yourself to, are off by one generation, you are "once removed." This would apply to parent/child relationship. (See the orange lines on the tree.)

  1. The easiest example of a one generation difference is uncle and nephew. My GG Grandfather Karsten S. Tonseth was the nephew of Ernst Tonseth, Jr. (EAJ to his family). Karsten S. and Haakon Tonseth are first cousins, because they are the sons of the two brothers.

  2. After you get past the uncle/nephew level; Karsten W. Tonseth is the First Cousin Once Removed (1C1R) to Haakon Tonseth. Karsten W.'s parent is a first cousin to the parent of the target individual (Haakon Tonseth) so they are once removed. Another way to say it, they are one generation apart from the direct relationship to the target person.

  3. The pattern repeats down the line. If your parent is at the same generation level as your target person, you add 1R to their relationship. No matter what their relationship is, 1st/2nd/3rd cousins, just add once removed to that relationship and you have it figured out. Example: My father R.G. Tonseth and K. Tonseth's children are 3rd cousins (3C) straight across, and I am one generation removed (1R). Which makes our relationship, 3C1R.

  4. Additionally, this is the exactly the same process if your child is at the same generation level as your target person. If R.G. Tonseth is looking at my relationship to K. Tonseth's grandchildren, we are 4th cousins (4C) across the tree. R.G. Tonseth is 1 generation removed (1R) from this relationship, which makes their relationship, 4C1R.

Two Generations Apart (Twice Removed or 2R)

Are you ready for more? The pattern you learned with once removed, just repeats itself over and over.

Remember people at the same generation level are either siblings or cousins of some kind (1st/2nd etc).

One generation removed (1R), is the relationship between your parent/child and the "target" person.

Two generations removed (2R), represented by the green line on the family tree is the relationship between your grandparent/grandchild and the "target" person.

  1. The easiest relationship to understand is again, the great uncle/aunt to great nephew/niece relationship. On this tree, Karsten W. Tonseth is the great nephew of Ernst A. Tonseth, Jr. and vice versa.

  2. Now look at my father R. G. Tonseth, and Haakon Tonseth to determine their relationship. Find Haakon on the tree and then look at across to my branch and you can see that Haakon and Karsten S. are first cousins(1C). R.G. is the grandson of Karsten S. and because of that, he is two generations removed (2R) from this first cousin relationship. Hence, first cousins twice removed or 1C2R.

  3. If you want to find my relationship to K. Tonseth, follow the same path. Find K. Tonseth on the right hand branch of the tree and see what his relationship is to my branch of the tree at the same level. He is the 2nd cousin(2C) to my grandfather Karsten W., and I am 2 generations away from my grandfather (2R). Which means we are second cousins, twice removed or 2C2R.

Three Generations Apart (Thrice Removed or 3R)

Hopefully you are seeing a pattern now, and it is starting to make sense. Now that we are moving farther away from generation 0, there are only 2 people on the tree with the pink lines, or 3 generations removed. Three generations removed is looking at your great grandparent/child relationship to that of the target person. Since the chart is showing 6 generations, only my dad R.G. Tonseth and I are in this category.

  1. Looking at the non-cousin relationships for a three generation difference. R.G. Tonseth is the great grand nephew to Ernst A. Tonseth, Jr.

  2. I am the first cousin, thrice removed (1C3R) to his son Haakon Tonseth. To figure that out, find the target person (Haakon) and his relationship to the person at the same level in my direct line. He is the first cousin(1C) of Karsten S. Tonseth and I am three generations down from Karsten(3R).


The nomenclature of "removed" cousins is confusing to many people, and frankly, it took me working out this family tree to finally understand it. "Removed" is another way to specify how many generations up, or down the tree you are in relation to each other.

Remember, the fastest way to figure out how you and your "cousin" are related is to follow these steps.

  1. Identify the most recent shared common ancestor between you and your target person. This person is generation zero.

  2. Draw a simple family tree that connects you and your cousin to your common ancestor, clearly outlining the two branches. Make sure your tree continues until both of you are accounted for on it.

  3. Look at the position of your cousin on this tree, are you both at the same generation level? If so, subtract "1" from the generation level and you are that cousin level number without any removal. (1st/2nd/3rd/4th etc.)

  4. If you are different generation levels, find the target person and identify their relationship to your direct line ancestor. Now, count how many generations away you are from that ancestor and that is the number for the removed setting.

Other Resources

There are lots of cousin charts and calculators online that can also be used, if you would like to see other ways of determining relationships follow the links below:

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