# How many cousins share my 5th grandparents?

Matching DNA has put me in touch with an extremely large number of Norwegian cousins who share my fifth grandparents from Fatland farm on Halsnøy Island in Hordaland, Norway. What’s more, perhaps due to the large number of them, I am seeing some triangulation of segments among their results.

Halsnøy Island in Hordaland, Norway from the ferry

This started me thinking about the effect of many generations of big family sizes on the number of sixth cousins I might have from a specific set of 5th grandparents. It would seem to me that the larger the number of cousins, the more likely it is that there are some who share good sized segments with me and Dad.

So I did a little simulation in a spreadsheet. It’s very simple, it assumes that the number of children reproducing in every generation is the same so that you can see the differences for different family sizes. I also did a line or two with the real/estimated numbers from the Fatland couple.

If your family consistently had two children who had two children reproducing for six generations you would only have 64 fifth cousins, but if everyone in your family had six children who had six children then you have almost 50,000 fifth cousins. Quite a difference!

# Results in from my Double 3rd Cousin!!

According to family lore, when their business needed money my great-grandmother Charlotte Langermann Thannhauser, on my German Jewish side,  fixed up her sister Lina with her husband’s half brother in order to get Lina’s dowry invested in the family enterprise. Not such an uncommon occurrance. I was able to convince Lina’s great-granddaughter on the straight maternal line to test at 23andme. She is almost doubly my third cousin, sharing DNA from the Thannhauser and Langermann lines but not Engel.

# We have results from a first cousin

One of my cousins (half Norwegian) on Dad’s side (all Norwegian) just got his results. So I made this chart comparing myself to my 1st, 2nd, and 3rd cousins on Dad’s side. Mind you, the 2nd cousin is on Dad’s paternal side while the third cousin is on his mom’s side.

Kitty’s DNA versus her cousins

My brother’s chart looks very similar except no X match of course. Notice the very large X match I have with my first cousin which would come from his mother and my Dad’s mother, 57.3 cM. Interesting to see this as compared to my Dad ….