The Bombshell

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On 10th June 2020, I looked at my DNA matches and saw my 1st cousin there, matched at 6% to me. Now, if you don't know much about dna this may not seem alarming, but if you follow me through some simplified DNA maths, I will show you why I was concerned;

• You get 50% of your DNA from each parent, you are literally half one parent, half the other.
• You share around 50% of your DNA with your full siblings (share both parents), but in practise this can be a range of more like 35-65%
• You share around 25% of your DNA with your parents' full siblings, as well as the children of your own full siblings, but again this range can be slightly wider. You may call these people your Nieces, Nephews, Aunts or Uncles but the genealogical term is actually "nibling" which I definitely think we should use more in day to day life!
• You also share approximately 25% of your DNA with your grandparents, grandchildren, and half siblings (share one parent, mother or father not both)
• Your great grandparents, great grandchildren, 1st cousins (children of your parents full siblings), great aunts/uncles (grandparents full siblings) and your half siblings' children share around 12.5% of their DNA with you.

My 1st cousin matched me at 6%, not 12.5. In fact, he matched my Dad at 12.4%! I knew straight away that my Dad, and his brother, my cousin's father, could not have been full siblings.

Immediately, it occurred to me that Dad did not look like his father, brother or sister. He was a different build, bone structure, hair colour etc. I realised that it was very likely my Grandpa did not father my Dad, despite the birth certificate stating that he did.

If Grandpa wasn't Dad's Dad... Who was?

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