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Eliminating lines through DNA

Discussion in 'DNA Questions and Answers' started by sunflower, Jul 25, 2020.

  1. sunflower

    sunflower LostCousins Member

    This may seem a basic question but I would like confirmation from more informed sources than my own guesswork as I seem to be going round in circles. At night, in bed, I am convinced I have it sussed but when looking at it in the cold light of day, I am mistaken.

    I have identified a very close line to me, my sister and nephew (brother's son) which did not feature in my tree before my dna test. As it is so significant, I have to assume that one of my researched lines is not a genetic line. Therefore I am going through the very slow process of identifying matches to my tree to verify that the line is genuine. If I have matched with at least one other person say a great great grandparent, can I assume that the line is pure to the present day. Most of my matches (apart from immediate family) are with 3 or 4, sometimes 5 times great grandparents. The dna match in question is very much more recent, Ancestry states 1st - 2nd cousin. This person is 2 generations younger than my sister and I, so not sure which set of great grandparents or grandparents I should be looking at, or is my parents.? Can someone please give me guidance?
  2. Tim

    Tim Moderator Staff Member

    Hi Sunflower,

    I think you need to provide more details first so that people can give some thoughts.

    What cMs do you share with each of the people you mentioned?
    Why do you think there is 2 generations, because Ancestry states 1st - 2nd Cousin?

    I not sure why you make this statement
    Surely what you have is a new line which is not on your tree currently?

    If this person is your 1st cousin then you share the same Grandparents. Which would suggest that one of your aunts or uncles had a child which you don't know about.
    If this person is your 2nd cousin then you share the same Great Grandparents.
  3. peter

    peter Administrator Staff Member

    IMPORTANT: Anyone with such a close unexpected match should be very wary of posting details on an open forum (which this is). So the less detail the better - let's talk about it in general terms since that's the best way to ensure the discussion will help others faced with a similar conundrum in the future.
  4. sunflower

    sunflower LostCousins Member

    I thought I had replied in general terms but obviously not as my responding post was not allowed. It would have helped with future posts, to know where I went wrong and overstepped the mark in my generalisation. I have no copy of that post to re-examine and work it out for myself.
  5. peter

    peter Administrator Staff Member

    sunflower, I've sent you a private message with a copy of your post. My primary concern was that you gave precise details of matches, details that would allow the people you have been matched with to identity themselves.

    DNA discussions in public should be primarily about principles. As soon as you give information that could either identify other people or allow them to identify themselves you're at risk of breaching their privacy - and because it simply isn't necessary, it's a needless risk.
  6. Tim

    Tim Moderator Staff Member

    One approach is to produce what people call "a quick and dirty" research tree. You can create this tree in Ancestry but make sure it's private and non searchable.

    Expand the new match back to the same periods as your grandparents and great grandparents. See if any of these people where in the same place at the same time. It's sounding more like an NPE or a child given away to adoption?

    So this is a new line and not one of your existing known descendant lines from your ancestors.
  7. peter

    peter Administrator Staff Member

    Not at all. It's possible, but it's also possible that one of your ancestors or one of their brothers was 'playing away'.

    There's a coloured chart in my Masterclass from which you can work out all the possible relationships. Bear in mind that in most cases you're going to be matched with a half cousin, not a full cousin.
  8. sunflower

    sunflower LostCousins Member

    I have done this but on my offline tree but through a different connection altogether.

    The families concerned lived at completely different areas of Britain. Unless one visited the are of the other, there is no apparent connection. There must have been though, so I will keep trying to find it.

    Yes that is correct. I am pretty sure which side of my parents family it is through the process of elimination, which does narrow it down.
    I had another good match with someone on another site but couldn't find any connection until I compared matches on Ancestry and now find that both families share a common link with each other. That is something positive and I now only have one larger mystery family to fit into my tree.

    If I could determine the likely generation, it would help enormously but not being able to quote exact cMs, it is more difficult.

    Thanks for your help Tim, it is appreciated.

    This is the most likely answer and I have tried to pin it on one them but not been able to. My grandfather was the only male in his family but I am thinking it would be a female in my family that introduced the other family's dna. Three of us in my family have this other family's dna. I would lose a line if it was through the female line as I wouldn't be connected to her researched paternal line so I would have to swop it to the new line. If it is a half relationship, it wouldn't change anything in my direct line. Is that correct?

    This is a very useful chart and I use it a lot, even encapsulated it so it stands on my desk all the time. I think I have narrowed it down now, knowing the generational gap between us. So even if you haven't given me the exact answer, it has concentrated my mind on the relationship.

    Thank you for your help Peter.
    Last edited by a moderator: Jul 28, 2020

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