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Ancestral Family Tree DNA Testing / 3C or half 3C?
« on: Thursday 23 May 24 16:29 BST (UK) »
Hi everyone,
I have three DNA matches on Ancestry who all share a great grandparent couple. They are all from the same generation and two of them are brother & sister.
I believe I am related to their great grandfather. Indeed he attended my grandmother's christening in 1905 and acted as her sponsor. Now there is a possibility that the gentleman and my great grandmother might be half siblings rather than siblings so I wanted to test the theory using "The Shared cM Project 4.0 v4".
I have put my shared cM results below;
1) cousin X, 149cM, 3C = 17% probability, half 3C = 6% probability,
2) cousin Y (brother), 60cM, 3C = 22% probability, half 3C = 30% probability,
3) cousin Z (sister), 63cM, 3C =23% probability, half 3C = 32% probability.
So taking the brother (Y) and sister (Z) together one might assume we are half 3C but the addition of the other cousin (X) gives a more balanced result. As these cousins are all from the same family, sharing a great grandparent, I am taking the view that the low result of 6% for cousin X with whom I get the closest result (149cM) is telling me that 3C is the best overall description for all of the three cousins. This would indicate that my great grandmother and the great grandfather are full siblings and that my cousin matches are full 3C.
Does this sound reasonable?
Thanks in advance.
pughcd
I have three DNA matches on Ancestry who all share a great grandparent couple. They are all from the same generation and two of them are brother & sister.
I believe I am related to their great grandfather. Indeed he attended my grandmother's christening in 1905 and acted as her sponsor. Now there is a possibility that the gentleman and my great grandmother might be half siblings rather than siblings so I wanted to test the theory using "The Shared cM Project 4.0 v4".
I have put my shared cM results below;
1) cousin X, 149cM, 3C = 17% probability, half 3C = 6% probability,
2) cousin Y (brother), 60cM, 3C = 22% probability, half 3C = 30% probability,
3) cousin Z (sister), 63cM, 3C =23% probability, half 3C = 32% probability.
So taking the brother (Y) and sister (Z) together one might assume we are half 3C but the addition of the other cousin (X) gives a more balanced result. As these cousins are all from the same family, sharing a great grandparent, I am taking the view that the low result of 6% for cousin X with whom I get the closest result (149cM) is telling me that 3C is the best overall description for all of the three cousins. This would indicate that my great grandmother and the great grandfather are full siblings and that my cousin matches are full 3C.
Does this sound reasonable?
Thanks in advance.
pughcd