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Fourth cousin query

Discussion in 'DNA Questions and Answers' started by Kate, Dec 3, 2023.

  1. Kate

    Kate LostCousins Member

    Hello, perhaps someone with more knowledge than I have could help, please? I have a match of 32 cM across 2 segments on my maternal side. This lady is my 4 cousin 1 removed. We both researched our trees independently and I have known of her for some years.
    When I looked at shared matches, she matches 51cM with a lady on my paternal side, also a fourth cousin. This family came from Kent, whereas my other family are from Suffolk and Norfolk.
    Should I just think of it as a glitch in the DNA test results, as if it was 20cM or below I would have ignored it?
    Or is it worth digging around on my Suffolk lady's father's side to find a link with my Kent family.
    I hope this is clear and that someone can reply in simple language that even I can understand. I have asked her and as yet she is not aware of a connection. Thank you!
     
    Kate, Dec 3, 2023
    #1
  2. peter

    peter Administrator Staff Member

    I imagine that, like most of us, you tested your DNA to knock down 'brick walls'. If you are, in fact, closely-related to this lady on both sides of your tree then it could make it more difficult to collaborate with her on the 'brick walls' you share - however, there's no reason at this stage to assume that this is the case.

    The fact that she is a DNA match for someone you are connected to on the other side of your tree is probably just a coincidence. You have thousands of matches on each side of your tree, and so does she - there are bound to be some that you share purely by chance.

    I suggest focusing on the matches that might help you knock down your 'brick walls', ie the matches that you identify using the strategies in the Masterclass. Curiousity is generally a good thing, but if we spend all our time trying to work out how we are related to our closest DNA matches there will be no time to knock down those 'brick walls'!
     
    peter, Dec 3, 2023
    #2
  3. webwiz

    webwiz LostCousins Star

    You and your 4th cousins share one of 16 pairs of 3G-grandparents. Not many researchers know all of these and I would hazard a guess that hardly anyone knows them and has confirmed it with DNA. So many people will have parents who are relatively recent cousins without knowing it. In the era when our 3g-grandparents lived many people never left the location where they were born and a degree of consanguinity was common. If you ever managed to complete a full family tree going back 5 generations with all descendants you might solve your puzzle.

    Furthermore Suffolk & Kent were not as remote in early Victorian times as you might think. I have families who lived, worked and married either side of the Thames in Essex and Kent. It was much simpler to get a ferry across than to travel any distance by road. So to get from Suffolk to Kent only involved crossing Essex.
     
    webwiz, Dec 3, 2023
    #3
  4. peter

    peter Administrator Staff Member

    Reading webwiz's comments I realised that I didn't properly explain the key issue in my earlier post. Your original question seemed to suggest that there were only two possibilities - one that there was some sort of glitch in the DNA results, the other that you are related to this cousin on both sides of your tree.

    In fact the most likely answer is that the match between your two cousins has nothing to do with you - it is in a part of their trees which they share but you don't.

    A couple of years ago I wrote about a similar discovery in the newsletter - I had discovered that I was related to my cousin's widow. This didn't mean that the two of them were related, or indeed that my parents were related (the connections were on the opposite sides of my tree). It was just a coincidence - a happy coincidence.
     
    peter, Dec 4, 2023
    #4
  5. Kate

    Kate LostCousins Member

    Thank you Peter and Webwiz. I do have all 16 of mine and my reason for taking a DNA test was to confirm my paper research, which to some extent I have, and a couple of possible ancestors, which I have. I don't totally understand Peter's second comment but believe I am right in thinking there is a genuine connection but it's probably not worth looking for it. I do read the newsletters but unfortunately don't recall the widow discovery to which Peter refers. Thanks.
     
    Kate, Dec 4, 2023
    #5
  6. webwiz

    webwiz LostCousins Star

    Well done Kate in finding all your 3g-grandparents. You may be much younger than me, but all my paternal greatgrandparents were born before 1837 as were all my 2g-grandparents on both sides, and I have an illegitimacy on both sides and I have some common surnames. So I have not got back to my 3g-grandparents on 3 lines and I use DNA more to confirm my paper based research than to knock down brick walls. Some lines do go further back and one leads to a gateway ancestor who is a direct descendant of William the Conquorer according to published genealogies of the aristocracy. William is just one of my 134 million 27g-grandfathers (ignoring duplicates, in reality probably a few hundred thousand different men) so it is unlikely that I carry any of his DNA at all. DNA rapidly loses its usefulness as one goes further back but is much more reliable in recent generations, and nobody can ever be completely certain that paper research has revealed the truth about their ancestry.
     
    webwiz, Dec 4, 2023
    #6
  7. Kate

    Kate LostCousins Member

    Possibly I am younger then but I haven't found anything as exciting as a gateway ancestor....yet!
     
    Kate, Dec 4, 2023
    #7
  8. Tim

    Tim Megastar and Moderator Staff Member

    upload_2023-12-4_22-51-3.png
     
    Tim, Dec 4, 2023
    #8
    • Agree Agree x 1
  9. peter

    peter Administrator Staff Member

    It's important that you do understand my previous post - 0therwise you risk misinterpreting shared matches. What do you mean by "a genuine connection"?
     
    peter, Dec 5, 2023
    #9
  10. Kate

    Kate LostCousins Member

    By genuine I mean that there is a DNA match unlike when it is below 20cM and we might just be from the same area geographically. Or am I completely wrong?3
     
    Kate, Dec 5, 2023
    #10
  11. peter

    peter Administrator Staff Member

    Yes, it's definitely a genuine DNA match.

    But so too are the vast majority of matches below 20cM - Ancestry don't use 20cM as the cut-off point for shared matches because matches below that level aren't likely to be genuine! (Their actual cut-off point is 8cM; previously it was 6cM, but their research found that half of 6cM matches were spurious.)

    I will try to explain again where you are going wrong. Suppose that you are A, the lady who is a cousin on your mother's side is B, and the lady who is a cousin on your father's side is C. You seem to have assumed that if your matches with B and C are genuine, then because B and C also match each other, that connection must have something to do with you.

    That isn't the case - you only share 1/16th of your tree with a 4th cousin. So the connection between B and C could well be in the 15/16ths of their trees that they don't share with you.

    So there are two possibilities - either it's just a coincidence that B & C are related to each other, as well as to you, or there is an additional connection between yourself and one of them that you have yet to find.

    In your first post you pointed out the geographical disparity - this greatly increases the chance that the match between B and C is just a coincidence. And as I explained earlier, with 5000+ DNA matches on each side of your tree there are bound to be some of them who match with each other - after all there are over 25 million (5000 x 5000) potential connections between them!

    Here's another way to look at it. LinkedIn frequently suggest someone (C) who I might know, based on the fact that they are connected to one of my existing connections (B). If I do know C there are two possible reasons - one is that I know them for the same reason I know B, for example, because they are both genealogists.

    The other is that I have completely different reasons for knowing B and C. So the reason that B and C know each other might have nothing at all to do with me. They might have grown up in the same street, they might have met at university, they might share some obscure interest. In other words it could just be a coincidence that I know both of them.

    It's the same with your DNA matches.
     
    peter, Dec 5, 2023
    #11
  12. Pauline

    Pauline LostCousins Megastar

    I refer to this scenario as ‘relatives in common’, and in case it’s helpful, here is an example from my tree:

    My 3rd cousin John and I share a set of 2 x great grandparents in Kent, supported by documentary and DNA evidence. At the same time and purely by coincidence, each of us, on the other side of our trees, has ancestors in the same town in Gloucestershire, but we do not have any shared ancestry in Gloucestershire.

    Purely by coincidence, the niece of one of John’s Gloucestershire ancestors married the nephew of one of mine. The descendants of that marriage are related to both us. A living descendant (say Ann) would be a DNA match to John and to me, so Ann would show up in our shared match list. However, because Ann is related to John via the niece and to me via the nephew, the three of us do not share a common ancestor.

    I hope that makes sense, and it provides an example of how a match may shared by coincidence rather than indicating another common line.
     
    Last edited: Dec 5, 2023
    Pauline, Dec 5, 2023
    #12
    • Agree Agree x 1
  13. Kate

    Kate LostCousins Member

    Thank you, I understand that.
     
    Kate, Dec 5, 2023
    #13

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