Third cousin once removed/4th cousin

[strictlysnoopy]

I have had a request from a DNA link to find a common ancestor between us.  She is a third cousin once removed or a 4th cousin, we share a 29cm across 3 segments.
My question is do I start with a 3xgreat grandparent or a 2xgreat aunt.  or have I read the table wrong?
  Thank you

[QueenoftheWest]

Hi,

I am by no means a DNA expert but I thought I would share with you a few things I have learnt from my experience trying to link DNA cousins to my mother's family tree (she took the DNA test for me so the results would be stronger).

DNA inheritance is incredibly random, especially that far back. You can have 3rd cousins with whom you may not share enough DNA for the relationship to be detected (between 2-10% chance of this happening according to International Society of Genetic Genealogy) and 2nd cousins who share so much DNA with you, the chart indicates that there is only a 22% chance they are your second cousin and a 77% chance they are your 1st cousin, once removed (happened to me). In all honesty, I would use the 'tables' provided by the autosomal testing companies as a very rough guide, especially with matches under 50cM. Most of the time, I find they are actually incredibly inaccurate so I just ignore them.

As an example, I have a 31cM DNA match who is my mother's 4th cousin, once removed. According to the table, there is only a 6% probability of this being the case. It is unlikely that your DNA match is exactly what the table suggests.

My recommendation to you would be:

• Make your tree as complete and accurate as possible (back to the 1700s at least). Ask RootsChat if you need any help.
• Look at your DNA match's tree (Person 1) and, if it is patchy in places, create your own tree for them.
• If you see a shared ancestor, great! If not, continue with the steps below.
• Look at the matches you and Person 1 share and see whether you can identify your link to the shared match using step 1 (with the shared match this time) and 2.
  If you can identify a common ancestor between you and one of your shared matches: use this information to identify which side of the tree you should be looking at. For example, if you both share a 3xGG Mr Smith from Farnham then look at Person 1's tree to see whether any of their ancestors came from this area. This will make it much easier and is it will cut down the amount of lines you need to explore.
  If you cannot identify a common ancestor: look at the locations instead. Do you recognise any?

The best way to identify how you are related to this person is to use your family trees, not the 'table' suggestions. Once you have identified a common ancestor, it is easy to work out how you are related.

Queenie

[exeter dweller]

I have a 29cM match who is a third cousin.
I have other matches around 25cM who are 5th cousins.
Depends on how much DNA you inherit from each parent grandparent etc.

[phil57]

The tables only indicate the likelihood of probabilities. The only people you can actually start with are you and your match, and work back. If you both have well developed trees, the connection between you may be fairly obvious or not too difficult to resolve, but if either of you haven't, you need to research backwards through either or both trees until you find the connection.

One of my highest matches is a person with a tree on Ancestry. It consists of the names of his parents and two grandparents. I have inferred his name from his account name and his parents names, since he hasn't been on Ancestry for some time and I've had no response from him. Despite my efforts to research his tree back several generations on both sides of his family I'm no nearer to having any idea how we match, and from the lack of information in his tree I have a suspicion that even if I could contact him, he might not have either.

[strictlysnoopy]

Firstly a huge thank you to you all for taking the time to reply.  This linking DNA matches is really a matter of loads of patience and just the perfect little hint or find that pulls it all together.
    Both our trees, on a particular branch go back to 1780's or so.  We have each a  3rdggrandfather, coming from the same area, both with the surname Williams (in Wales),  all children from their marriages have the same or similar christian names, Richard, William, Henry and Edmund, BUT there is the dreaded brick wall, we cannot link them, mainly because finding a baptism for one of them is just not happening, are they brothers who knows, hopefully time will tell.  We then turned to the wives to see if one of the wives was a Williams before she married, success.  Again no mention of a sibling called Richard.   So that is why I posted this question to see if there was another way we could go with the tables as a rough guide and our DNA result.
    Keeping our fingers crossed, one day all will be revealed.