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  • Family Finder yields

    Have you ever wondered how many of your potential Family Finder matches actually show up on your match list? As you know, your mother gives you half of her DNA and your father gives you half of his, so half of your parents' DNA isn't a factor in DNA matching here at FTDNA. The result is that your match list doesn't actually show everyone in the database to whom you are potentially related.

    Here are some numbers based on an actual family of three siblings:
    • Each sibling's match list shows just over half of the total matches for the three of them together. This makes sense given that each person carries just half of the parental DNA.
    • Therefore, looking at just one match list means not seeing nearly half of the total matches.
    • Just over 11% of the total matches show up on all three match lists. In any given list, 20-23% of the matches are shared with both of the other two siblings.
    I welcome anyone else's numbers from their sibling experiences.

  • #2
    I have a pie chart that I found some time ago, but don't know where. It shows the coverage of a parent's DNA, based upon how many of the siblings were tested. If you have enough siblings, you can cover almost all of the DNA passed down by the parents. Below, six siblings are shown, covering 99%.

    I don't think I've done a comparison, as you show, for the sibling groups who I have had tested at FTDNA, but I'll look through my files to check.

    parental_DNA_coverage_by_no_siblings_tested_FB.jpg

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    • #3
      There are five siblings in our family. In our combined match list...
      29.3% match one
      30.9% match two
      29.0% match three
      9.3% match four
      1.5% match all five

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      • #4
        One more detail I forgot to mention regarding my family of three siblings. Out of their total unduplicated matches, 53% appear in just one list or another. That is, each of the siblings has a number of matches that don't appear in the other two siblings' lists, and those unique matches add up to 53% of the shared total.

        And thanks to KATM for the wonderful pie chart!

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        • #5
          Originally posted by stennor View Post
          Have you ever wondered how many of your potential Family Finder matches actually show up on your match list?
          I suppose I don't think of it the way that you put it. What you phrase as "potential matches" I take to mean people who would be related to our parents. We know that we haven't inherited all the potential DNA segments that our parents could possibly have passed down to us, and that any siblings of ours who have tested would have inherited different segments from our parents, and therefore have different matches that we don't. This is the benefit of having siblings test their autosomal DNA all at the same company.

          While it may be interesting to compare the match lists of siblings to filter out the differences, it seems to me that it would be a better use of time to merge the match lists of a sibling group and remove duplicates, in order to represent most or almost all of the matches that the siblings' parents would have had, if they had tested. Of course, testing siblings and merging those lists could be avoided if both parents had done Family Finder testing, but not many have the chance to do so.

          Here is a useful table from Ancestry.com, showing how likely it is that your close family members would have a DNA match with a cousin with whom you don't share DNA. For this topic, we can just look at the Sibling column:

          AncestryDNA_chart_how likely_wd_fam_members_match_cousin.jpg
          Note how this table shows how other close relatives who have done Family Finder or similar tests, such as Uncles/Aunts, etc. often have a better chance than siblings of matching distant cousins. It is beneficial if you can have these other relatives tested, as they will many times pick up even more matches related to your ancestors.

          The vast majority of our matches range from 3rd cousin to more distant (8th?), so the possibilities of sharing a match in common with a sibling are less as the degree/distance of cousin increases. Therefore, if we have siblings tested, it is very likely that they will share segments with some of the many distant cousins with whom we do not share any segments (and vice versa). We have the highest percentages of having the same matches as our siblings with the closest degrees of cousins (2nd/3rd) and other close relatives. We have about a 90% chance of sharing with a 3rd cousin or 2C2R (per the DNA Detectives Autosomal Statistics Chart, and other sources), thus a 10% chance of not sharing. So, among siblings, some may begin to have matches with some 3rd cousins, which other siblings do not.
          Last edited by KATM; 18 April 2021, 01:31 PM.

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          • #6
            Wow! This is useful in tracing back my ancestry. Just to know first who are my relatives and how I'm connected with them.

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            • #7
              Originally posted by raspchide View Post
              Wow! This is useful in tracing back my ancestry. Just to know first who are my relatives and how I'm connected with them.
              Indeed, I've been using that table too, and to make life easier, you can the apps about DNA ancestry tests. There are reviews saying that the results are accurate.

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              • #8
                Originally posted by KATM View Post
                I have a pie chart that I found some time ago, but don't know where. It shows the coverage of a parent's DNA, based upon how many of the siblings were tested. If you have enough siblings, you can cover almost all of the DNA passed down by the parents. Below, six siblings are shown, covering 99%.

                I don't think I've done a comparison, as you show, for the sibling groups who I have had tested at FTDNA, but I'll look through my files to check.

                parental_DNA_coverage_by_no_siblings_tested_FB.jpg
                Thanks KATM for sharing this. Does the 1st child always have the biggest percentage?

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                • #9
                  It's not that the first child has a bigger percentage, it's just that the other children share overlapping DNA segments with their siblings. Each child received 50% of his or her DNA from the parents, but not the same 50% for each child. The additional percentages on the chart are meant to show the additional DNA from the 100% of each parent that is covered when more than one sibling is tested. Each sibling will vary as to which segments are shared with each other sibling, based on which segments each inherited from their mutual mother and father.

                  Since all the siblings have overlapping shared segments with each other, then cumulatively as you add a second, third, and more siblings in any order, each one will add more DNA segments from the parents which are not shared by the previous siblings; the amount added is increasingly smaller, since the overlapping shared segments with the other siblings have already been covered.

                  What you see on the chart is how much of 100% of either parent's DNA is covered, depending upon how many siblings are tested. It doesn't matter which child is tested first. If you have enough siblings, there will be enough unique segments which the other siblings did not inherit, to add toward the 100%. The chart adds up to 99% for 6 siblings tested; I don't know if that is approximate or not, but 99% is very close to representing 100% of the DNA of each parent. It is a substitute for parents who did not do DNA testing. Some, or even only one of the siblings, will have DNA matches which the others will not have. Whether or not such coverage will get all the DNA matches a parent would have matched is another question.

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                  • #10
                    Since I manage kits for a set of six full siblings, here is how one of the five sisters (call her the "base") matches to the other four sisters, plus their brother (at the 7 cM threshold).
                    • You can see how the brother (orange segments, or 4th in order) shares on the X with this sister, but not on the whole X, as the other sisters share. He may share other portions of his X if compared to another sister as the base.
                    • You can also see many instances of how the siblings share small parts of segments with this sister, where others share larger segments; and some areas where some share and others do not.
                    • On Chromosome 15, one sister (green segments, 3rd in order) does not share any DNA with the base sister; but on Chromosome 6 the same sister shares the whole chromosome with the base.
                    A different group of siblings might show different patterns, such as some having more complete chromosomes shared, or having more chromosomes where some do not share any DNA.

                    Comparison_sib1_to_sibs2-6.jpg
                    Last edited by KATM; 30 April 2021, 10:45 PM.

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                    • #11
                      Originally posted by Givert View Post

                      Indeed, I've been using that table too, and to make life easier, you can the apps about DNA ancestry tests. There are reviews saying that the results are accurate.
                      Okay bro, will definitely give it a try. Have you personally tried it? I've seen many post here about finding their ancestry and its inspiring!

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