Ancestry DNA question

[Flemming]

Shared matches will only show up in Ancestry shared match lists, if those matches match you at 20cM or more. So when you look at the shared matches for A, as B shares less than 20cM with you, it will not show on the shared match list, even though it is really a shared match between you and A. It doesn't make any difference as to how much A shared with B, you can't find that out unless you ask the persons, or ask them to share their DNA with you

https://support.ancestry.co.uk/s/article/Sharing-AncestryDNA-Results

I think the point being that the threshold for A and B sharing DNA does seem to be 20cM. I've got access to eight kits and also work with a few other matches and 20cM seems to be the magic number.

[melba_schmelba]

Shared matches will only show up in Ancestry shared match lists, if those matches match you at 20cM or more. So when you look at the shared matches for A, as B shares less than 20cM with you, it will not show on the shared match list, even though it is really a shared match between you and A. It doesn't make any difference as to how much A shared with B, you can't find that out unless you ask the persons, or ask them to share their DNA with you

https://support.ancestry.co.uk/s/article/Sharing-AncestryDNA-Results

I think the point being that the threshold for A and B sharing DNA does seem to be 20cM. I've got access to eight kits and also work with a few other matches and 20cM seems to be the magic number.

I am sure that the only number that matters is how much a kit matches you, it doesn't make any difference say...if you are X and match Y and Z is a shared match, how much Y matches Z has no effect on whether Z appears as a shared match between you and Y, only that Y matches Z at all according to Ancestry's minimum requirements (which may be 9cM single or multiple segments).

[Flemming]

Not sure I understand that totally 

The conclusion a few of us have come to is that, if you open a 9cM match (for example), you will only see matches you share with them if those matches share >20cM with both of you.

Maybe you have a different experience of this but this is pretty much what we're seeing over and over.

[decor]

Not sure I understand that totally 

The conclusion a few of us have come to is that, if you open a 9cM match (for example), you will only see matches you share with them if those matches share >20cM with both of you.

Maybe you have a different experience of this but this is pretty much what we're seeing over and over.

I suppose this is the crux of my original question. Whether you both have to share 20cM with the match OR whether only you has to share 20cM with the match, but the other person just has to match at all, even at 9cM.

[decor]

It just struck me that I manage my uncle's DNA results so I could test out the 20cM theory...and the results are clear.

When we both match someone over 20cm, we can both see each other in the shared matches.
When my uncle matches someone over 20cm but I match them under 20cM, I can see my uncle in the shared matches BUT he cannot see me.

So, in other words, the "other people" involved in the triangle have to match at 20cM or over for them to be visible.
Coming back to my original query in the thread, the sons of my paternal and maternal cousins may match people I also match but at less than 19cM, at which point they become invisible.

It's quite frustrating...and even just reducing it to 15cM would make a big difference already!

[melba_schmelba]

Not sure I understand that totally 

The conclusion a few of us have come to is that, if you open a 9cM match (for example), you will only see matches you share with them if those matches share >20cM with both of you.

Maybe you have a different experience of this but this is pretty much what we're seeing over and over.

Oh dear .....I also manage several kits, and I have just looked over a few examples and looking again.... I think you must be right  . So yes I think it must be that 20cM must be 2 way (but not three  ).