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Thread: Family finder 2/3rd cousin shared common ancestor.

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    Family finder 2/3rd cousin shared common ancestor.

    Hi if I find a 2nd to 3rd cousin via Family Finder, on what generational level do we share the most recent common ancestor? Ie. Do we share a great grandfather or grandfather etc?
    Thanks

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    Quote Originally Posted by Hando View Post
    Hi if I find a 2nd to 3rd cousin via Family Finder, on what generational level do we share the most recent common ancestor? Ie. Do we share a great grandfather or grandfather etc?
    Thanks
    Much of the time it will be just as you might expect: someone who shares G, GG or perhaps GGG grandparents with you (or equivalent if you're from different generations). At times the estimate can be wrong and the common ancestors are more distant. Broadly, if you're going through a lot of matches it's a useful indicator of shared ancestry in recent generations.
    Living DNA Cautious mode:
    South Wales Border-related ancestry: 86.8%
    Cornwall: 8%
    Cumbria-related ancestry: 5.2%
    Y line: Peak District, England. Big Y match: Scania, Sweden; TMRCA 1,280 ybp (YFull);
    mtDNA: traces to Glamorgan, Wales, 18th century. Mother's Y line (Wales): R-L21 L371

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    2nd cousin means shared g-grandparent, and 3rd cousin would be shared gg-grandparent. Also could commonly be your gg-grandparent and that person's g-grandparent (so 2nd cousin once removed).

    But also what JonikW says is right.

    My dad's closest non immediate family match on FTDNA is his 2nd cousin once removed (shows as 2nd-3rd). Others are very similar. However, on the first page is a match that shows as 2nd to 4th, and we are pretty confident that the only connection is that she is also descended from his gggg grandfather, which would make her a 5th cousin.

    That match and my dad have another common match who shows as 2nd-4th of my dad, 4th-6th of my sister on Ancestry, and we haven't managed to find the connection at all, even though we know from common matches what lines they are on, and both lines are known pretty far back (and the match is a good researcher). The locations mid-1700s (when the gggg grandparents that connect my dad to the first match were born) are about 10-15 miles apart in Essex. (Could be an NPE, of course.) This is my current fascination or frustration.
    Last edited by msmarjoribanks; 01-17-2019 at 11:58 PM.

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    There's a tool that's actually pretty handy when it comes to trying to determine relationships. It's "The Shared cM Project 3.0". There are actually several versions of the tool, such as v4, which you can find here: https://dnapainter.com/tools/sharedcmv4.

    With this tool (or one of the other versions), you can get an estimate of the degree of sharing by just "plugging in" the total amount of DNA shared. Often, you'll see percentages for several possible different relationships, so the tool won't necessarily be able to tell you exactly what the relationship is -- just what the probabilities are.

    But you have to keep a couple of potential "complications" in mind. If you're using data from FTDNA, you should only use the total for segments over 5 cM in length. Also, keep in mind that you can be related to someone in more than one way.

    For example, I have a cousin who shares a pair of 2nd great grandparents with me. That makes us 3rd cousins. But he's actually descended from this same couple twice. Through his father, they're his 2nd great grandparents. But through his mother, they're his 3rd great grandparents. So I'm his 3rd cousin once removed, as well as being his 3rd cousin. (And, yes, I do share DNA with both of his parents.)
    Last edited by geebee; 01-18-2019 at 02:09 AM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

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    Quote Originally Posted by JonikW View Post
    Much of the time it will be just as you might expect: someone who shares G, GG or perhaps GGG grandparents with you (or equivalent if you're from different generations). At times the estimate can be wrong and the common ancestors are more distant. Broadly, if you're going through a lot of matches it's a useful indicator of shared ancestry in recent generations.
    Thanks to all three of you guys. The Family Finder Matches page states that my match and I share 161 centimorgans. And the longest block is 68.
    What is the probability that the 2nd to 3rd cousin estimate is wrong?
    Thank you

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    Quote Originally Posted by geebee View Post
    There's a tool that's actually pretty handy when it comes to trying to determine relationships. It's "The Shared cM Project 3.0". There are actually several versions of the tool, such as v4, which you can find here: https://dnapainter.com/tools/sharedcmv4.

    With this tool (or one of the other versions), you can get an estimate of the degree of sharing by just "plugging in" the total amount of DNA shared. Often, you'll see percentages for several possible different relationships, so the tool won't necessarily be able to tell you exactly what the relationship is -- just what the probabilities are.

    But you have to keep a couple of potential "complications" in mind. If you're using data from FTDNA, you should only use the total for segments over 5 cM in length. Also, keep in mind that you can be related to someone in more than one way.

    For example, I have a cousin who shares a pair of 2nd great grandparents with me. That makes us 3rd cousins. But he's actually descended from this same couple twice. Through his father, they're his 2nd great grandparents. But through his mother, they're his 3rd great grandparents. So I'm his 3rd cousin once removed, as well as being his 3rd cousin. (And, yes, I do share DNA with both of his parents.)
    Thanks for the link. I do not know how to read the Family Finder Matches page. It states that my match and I share 161 centimorgans. And the longest block is 68. Which number should I plug into the dnapainter tool?
    Thanks

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    Quote Originally Posted by Hando View Post
    Thanks for the link. I do not know how to read the Family Finder Matches page. It states that my match and I share 161 centimorgans. And the longest block is 68. Which number should I plug into the dnapainter tool?
    Thanks
    It's probably a 2nd or 3rd cousin or somewhere in-between (like 2nd cousin once removed). Any common matches? Do they have a tree? Surnames? I'd go to your gg-grandparents and trace forward, but common matches might make it easier.

    I can usually figure out what g-grandparents they relate to based on common matches. If they have no tree or surnames and I can't figure it out based on my own information I email them and say what I know and ask if they know or want to work together.

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    Quote Originally Posted by Hando View Post
    Thanks for the link. I do not know how to read the Family Finder Matches page. It states that my match and I share 161 centimorgans. And the longest block is 68. Which number should I plug into the dnapainter tool?
    Thanks
    Just look for the various relationships that match your total match -- https://dnapainter.com/tools/sharedcmv4

    Then maybe start with those where the average is closer to your amount.

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    Quote Originally Posted by msmarjoribanks View Post
    It's probably a 2nd or 3rd cousin or somewhere in-between (like 2nd cousin once removed). Any common matches? Do they have a tree? Surnames? I'd go to your gg-grandparents and trace forward, but common matches might make it easier.

    I can usually figure out what g-grandparents they relate to based on common matches. If they have no tree or surnames and I can't figure it out based on my own information I email them and say what I know and ask if they know or want to work together.
    Thanks again. Iíve emaiiled the person and am waiting a reply because they donít use any surnames. Just a nickname. And donít have a tree. But in the meantime Iím trying to figure out what probable kinship relationship they are. But I donít know which number to enter into the filter/box. Is it the longest block which is 68 or the 161 centimorgans which I share with my match. Sorry, but Iím new to the dnapainter.com link As well as all the lingo. It says to enter the total number of Cm of my match, but I donít know which it is.

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    Quote Originally Posted by Hando View Post
    Thanks again. I’ve emaiiled the person and am waiting a reply because they don’t use any surnames. Just a nickname. And don’t have a tree. But in the meantime I’m trying to figure out what probable kinship relationship they are. But I don’t know which number to enter into the filter/box. Is it the longest block which is 68 or the 161 centimorgans which I share with my match. Sorry, but I’m new to the dnapainter.com link As well as all the lingo. It says to enter the total number of Cm of my match, but I don’t know which it is.
    I would think that it's 161 cM you use since that is the total number of cM.
    Ancestry: Ireland (Roscommon, Galway, Mayo)
    Paternal ancestor (Y): Kelly b. c1830 in Co. Roscommon
    Father's mtDNA: Fleming b. c1831 in Co. Roscommon (H27e)
    Maternal ancestor (mt): McDermott b. c1814 in Co. Roscommon
    Paternal great grandfather (mt): Connella b. c1798 in Co. Roscommon (T2a1a8)

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