Puzzling shared DNA match

[LizzieL]

I tested with Ancestry a few years ago and uploaded my results to My Heritage among other sites.
A couple of weeks ago I got a common ancestors hint on Ancestry with GP (43cM). I checked through her tree and verified that our shared ancestors were my 3 x ggp on paternal side ( John Trevatt and Esther Child from Sussex). Today I had a message from My Heritage to say I had a new match. It was with GP, who had now uploaded her results to MH as well. I looked the shared matches which came up on MH and found a name I recognised from my Ancestry matches (KK 33.8 cM) as it is an unusual name.
The trouble is that Ancestry does not show up a shared match between me, GP and KK. In fact Ancestry has come up with a Common Ancestor hint with KK for 3 x ggp on my Maternal side (Matthew Wood and Elizabeth Addy from Yorkshire). Definitely same KK as he has photo and extensive tree on both sites.

I have two shared matches with KK on Ancestry, both verified as being descended from Matthew Wood and Elizabeth Addy. And one shared match on Ancestry with GP verified as being descended from John Trevatt and Esther Child.

Gedmatch has confirmed my parents are not genetically related to each other - not surprising as their Ancestors came from quite different parts of the country.

Has anyone else come cross this sort of anomaly?

[melba_schmelba]

I tested with Ancestry a few years ago and uploaded my results to My Heritage among other sites.
A couple of weeks ago I got a common ancestors hint on Ancestry with GP (43cM). I checked through her tree and verified that our shared ancestors were my 3 x ggp on paternal side ( John Trevatt and Esther Child from Sussex). Today I had a message from My Heritage to say I had a new match. It was with GP, who had now uploaded her results to MH as well. I looked the shared matches which came up on MH and found a name I recognised from my Ancestry matches (KK 33.8 cM) as it is an unusual name.
The trouble is that Ancestry does not show up a shared match between me, GP and KK. In fact Ancestry has come up with a Common Ancestor hint with KK for 3 x ggp on my Maternal side (Matthew Wood and Elizabeth Addy from Yorkshire). Definitely same KK as he has photo and extensive tree on both sites.

I have two shared matches with KK on Ancestry, both verified as being descended from Matthew Wood and Elizabeth Addy. And one shared match on Ancestry with GP verified as being descended from John Trevatt and Esther Child.

Gedmatch has confirmed my parents are not genetically related to each other - not surprising as their Ancestors came from quite different parts of the country.

Has anyone else come cross this sort of anomaly?

You say it is a shared match on MyHeritage, but MyHeritage, like 23andme, but unlike Ancestry, has no minimum threshold for shared matches, so you A, can match B, and have a shared match C, but C could match you down to 7cM (I think the lowest cM on MH), but B could match C at 299cM. So in that case a shared match could very likely simply be coincidental. Does it also show shared segments?

On Ancestry, A has to match C and B match C over 20cM for C to show as a shared match.

[LizzieL]

Yes I follow the threshold thing on Ancestry and if KK was also descended from John Trevatt and Esther Child, but the match was below 20, it would make sense. But GP and KK are from two different sides of my family. I have since found GP's sister is on MyHeritage and KK and I have a shared match with her as well. I haven't found GP's sister on Ancestry so she must have tested with MH or another company and uploaded to MH.

[melba_schmelba]

Yes I follow the threshold thing on Ancestry and if KK was also descended from John Trevatt and Esther Child, but the match was below 20, it would make sense. But GP and KK are from two different sides of my family. I have since found GP's sister is on MyHeritage and KK and I have a shared match with her as well. I haven't found GP's sister on Ancestry so she must have tested with MH or another company and uploaded to MH.

With Ancestry's SideView it is clearer that some smaller shared matches are probably coincidental, as I have noticed fairly often, that, say, you have match B that shows on your maternal side, then shared match C that shows as being on your paternal side. It is simply a coincidence, and means you, B, and C likely do not share a common ancestor.

[whoamitoday]

I've got something similar.
In my case it turned out that a first cousin four times removed on my paternal Devon side, sailed over to Swansea and married my first cousin three times removed on my maternal Welsh side. My parents aren't related, don't share any common ancestors, but share distant cousins who have descended from that couple.

[LizzieL]

I've got something similar.
In my case it turned out that a first cousin four times removed on my paternal Devon side, sailed over to Swansea and married my first cousin three times removed on my maternal Welsh side. My parents aren't related, don't share any common ancestors, but share distant cousins who have descended from that couple.

I have one like that too. Ancestry picks up the closer pair of shared ancestors on paternal side (2x ggp), but not the more distant CAs on maternal side.

[Biggles50]

There are two DNA matches to me on Ancestry who are also DNA matches to my Wife.

Comparing my Gedmatch DNA upload to my Wife’s we are not related to each other via shared DNA.