Should I ignore these DNA matches?

[pickpin]

I am working on a family tree where the paternal side is entirely unknown.  I've tried reaching out to the stronger shared matches via the Ancestry messaging service but most are still unread.  I've been able to plot out basic trees for the shared matches from what they have posted online themselves and am experimenting with putting their great grandparents into our tree to try to use thrulines to identify more distant matches to try to find where the shared ancestors might be.

For one of the close matches 217 cm are shared.  Thrulines suggested a 2nd great grandfather, who having checked the paper trail (census, births, marriages, deaths etc.) looks like the wrong guy (I've read that Thrulines can give rogue results so have been trying to double check them).  The name fits, but other aspects, such as children and parent names, dob etc. are wrong.  However, I have 3 DNA matches linking to this guy.  They are descendents of his siblings (each descends from a different sibling), so theoretically sharing a 3rd GGF.  The amount of DNA shared with these matches is very low: 8cm in 1 segment, 9cm in 1 segment and 14cm in 2 segments.  The last one I can see one of her ancestors is also related on the maternal side of my tree. I have a good tree on the maternal side and thus far all DNA matches have fitted with the paper trail.  Also looking at the shared matches with the 14cm person, they are all on my maternal side except the 217cm match and a very close relative of the 217cm match.  There are no shared matches with the 8cm and 9cm people.

I guess what I'm asking is could the two other matches (8cm and 9cm) be matching by random chance because they are so small?  Is there an amount of cm that we share with people by chance even if we are not distant cousins?

I find all this DNA stuff so fascinating, but as soon as I feel I'm making sense of things, something like this happens and I realise I really don't understand very much!

Grateful for any thoughts or insights!

[Galium]

I have a 3rd cousin 1x removed - my 2x great grandfather is her 3x great grandfather.  On Ancestry we share 6cm - and if we didn't already know our relationship and had it confirmed by Thrulines, Ancestry would have ditched that match when they had their clearout as being too low to be of importance.  I also have matches whose relationship to me is more distant, but the shared amount of DNA is greater.

So you can't be sure how close the relationship is just by looking at the number of centimorgans. 

Re your 217cm match - if you are sure about your paper trail, maybe theirs is inaccurate? 

[Gadget]

I find that Common Ancesters and Thrulines Evaluate are often wrong. Members' trees should also be thoroughly checked and sourced.

Have you used DNA Painter to look for other possible relationships to the 217cM match:

https://dnapainter.com/tools/sharedcmv4

[pickpin]

Thanks for your replies.  re the 217cm match - I have only been able to find one other match that fits in their family tree who is their nephew, so it's not enough for DNA painter to go to work with, hence why I'm trying to find some more distant matches.  I've retraced their ancestry up through this line to check it out and it seemed sound up to 2GGP, but I swapped out the 3GGP because it didn't fit with the census and birth records I could find and their only source was another member's tree.

I guess I'm not so much trying to work out how related these 8/9cm matches are, but more trying to understand whether I should be open minded to the possibility they aren't related at all (at least not without going back to the iron age or something!  )

[Gadget]

Painter suggests a numbe of possible relationships with  shared 217 cM   - See below


What you have to do, as many of us have, is to take teh parents and create his tree from scratch.

[Gadget]

...and with 8cMs shared

It can take a long time to work out. You need to work at your matches trees.  Don't rely on Odds, etc.

[Gadget]

Also consider NPEs (Non-Parental Events)

[pickpin]

I'm pretty sure there are NPEs at play here.  All the closest matches (100-500cm) have no shared ancestors on paper so I'm being really careful not to make assumptions, hence I don't want to assume these distant matches are relatives if that may not be the case.

[Biggles50]

At the lowest 4% probability that is a 3C at Great Great Grandparent level.

Do you have as wide a tree as possible at this level?

Including all offspring and brining each of them as far forward to present day as you can?

I have a 240cM match and my nearest fit is a NPE that produced my Great Grandmother.

A tree based upon the match which has a few others who are Shared does give the right relationships and DNA Painter’s WATO tool works well with my own hypothesis.

Conversely I have a 96cM match that is shared with other matches in my tree to my maternal Grandmothers side of the family and none have the match in their trees and despite building four different trees on the likely candidates no link has yet been found so I too am at the stage that in his past an NPE occurred and one if his forebears was secretly adopted.

So just stick at it, build a few standalone trees each based on likely candidates and wait to see what hints come in.

It may be a long shot but do upload your DNA data to the comparison sites on the chance that they to have done this and with the tools available on them it could be possible to narrow the options.