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I know this will sound far-fetched, but maybe someone can help me.

DNA Match through Ancestry shows:

  • 'First Cousin' match at 820 CM over 37 segments (Let's call him Tom)
  • 'Second Cousin' match at 541 CM over 32 segments (Let's call her Sue)
  • 'Close Family' match at 1408 CM over 59 segments (Let's call him J.D.)

What I know from contacting Tom:

  • 'First Cousin' (Tom) is the son of my great-uncle on my dad's side
  • 'Second Cousin' (Sue) is the full sister of (Tom)
  • 'Close Family' (J.D.) does not actually show a name, only initials, and his results are managed by 'Second Cousin' (Sue). I know nothing else about him.

Questions:

  • Why are Tom and Sue different levels of cousin (1st and 2nd) to me if they are full siblings?

  • How would J.D. be related to me?

  • Is it possible that my mother could possibly be the mother to one of these matches (a 1/2 sibling)? I know she had a 'creepy' uncle who she does not want to talk about, and on my birth certificate it shows there was one child born before me (she says it's a clerical error). If it helps, I am in my 50's and so are my matches (except J.D. whom I have no info about).

  • Tom isn't willing to tell you who J. D. Is? – Ellen Spertus Aug 15 '18 at 22:28
  • To me it sounds like your mom may not be telling the truth about the "clerical error". But I'm just speculating! – Katie Aug 17 '18 at 22:23
  • Just found out that J.D. is the father to Tom and Sue. He is 86 years old and my great-uncle (My dad's mother is J.D.'s sister). How can my great-uncle have such a high CM match to me? – Lexo Aug 29 '18 at 2:32
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Why are Tom and Sue different levels of cousin (1st and 2nd) to me if they are full siblings?

If Tom is the son of your great-uncle, he is your first cousin once removed (1C1R), as would be his sister Sue. According to the Shared Centimorgan Project, 99% of 1CRs (and equally related people) share 131-851 cM, so Tom and Sue could both be 1CRs (although Tom is likelier to be more closely related). What is important is the cM information, not Ancestry's guesses at relatedness.

How would J.D. be related to me?

It's impossible to say from the given information. When viewing your match with J.D., you can click on "Shared Matches" to see who is related to both of you. It would be worth knowing if both Tom and Sue are.

You might consider joining a group such as DNA Detectives, which helps people in situations like yours.

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  • Thank you for the insight. I will see if I can find more info for J.D. as you suggested :) – Leko Aug 15 '18 at 19:31

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