If we're related in more than one way ...

[Sue_3]

I have an Ancestry DNA match that I share 62 cMs with.

I think that they are descended from my 3* gt grandfather Thos A and his second wife Clarrie C, whereas I am descended from my 3* gt grandfather Thos A and his first wife Betty B.

The plot thickens because Thos A's second wife Clarrie C was also the daughter of my 3*gt grandfather John D and his first wife Hattie E. I am descended from John D and his second wife Mary F, via their son Freddie G. Freddie G Married Mary J, who was the daughter of Thomas A and Betty B.

I am attaching a quick sketch that may, or may not, help to follow all of that.

My 'Family Historian' software tells me that my match is BOTH my half 4th cousin AND my half 4th cousin once removed.

A further complication is that my great grandfather Fred H, who was the son of Freddie G and the grandson of John D and Mary F above, married a woman - my great grandmother Josie I - who was from a family where there was also pedigree collapse. On that line, my 9* gt grandmother is also my 7* gt grandmother, because two of her descendants married each other.

The DNA Painter shared CM tool doesn't seem to cater for half 4th cousin relationships, which suggests that they are unlikely to show up as DNA matches. However, given the pedigree collapse detailed above, is it likely that my match and I would share 62 cMs?

I have tried to follow the articles about pedigree collapse calculations that the DNA Painter site links me to, but maths is not my forte, so I wonder if anyone here understands it better than I do? If not I will persevere, but I thought it worth seeking advice before devoting many more hours to this problem.

Thanks in advance for any constructive input.

 

[Sue_3]

Btw, I have made up / altered all of the names to protect both the innocent and anyone who might have been guilty of causing so much confusion!

 

[Helen7]

The DNA Painter shared CM tool doesn't seem to cater for half 4th cousin relationships, which suggests that they are unlikely to show up as DNA matches.

I have a half 4th cousin once removed with whom I share 39 cM, and I share 16 - 29 cM with their 3 children (my half 5th cousins). I have a few other half 4th cousins and half 5th cousins who show up as DNA matches (albeit <20 cM), and if you are related to your DNA match in two different ways as you describe, that would increase the likelihood of your match.

 

[peter]

This is just another reason why I do not recommend using DNA Painter or other tools. Stick to the table and chart in my Masterclass - they have all the information you need.

 

[Sue_3]

I have a half 4th cousin once removed with whom I share 39 cM, and I share 16 - 29 cM with their 3 children (my half 5th cousins). I have a few other half 4th cousins and half 5th cousins who show up as DNA matches (albeit <20 cM), and if you are related to your DNA match in two different ways as you describe, that would increase the likelihood of your match.

That's very useful to know, thank you.

 

[Sue_3]

This is just another reason why I do not recommend using DNA Painter or other tools. Stick to the table and chart in my Masterclass - they have all the information you need.

Hi Peter, the 'shared CM tool' that I was referring to is the same chart as in your masterclass, it is Blaine Bettinger's chart, and it doesn't mention half fourth cousins, which is why I needed to ask the question. The table in your master class doesn't seem to mention half cousins at all? I also didn't find anything about pedigree collapse there? Apologies if I am missing something, which is very possible? I have the paper trail here, I am just trying to reconcile the number of shared cMs with that, to ensure the evidence is consistent. If the DNA evidence is not consistent with my other evidence, then more research is needed. Thanks, Sue

 

[peter]

Hi Peter, the 'shared CM tool' that I was referring to is the same chart as in your masterclass, it is Blaine Bettinger's chart, and it doesn't mention half fourth cousins, which is why I needed to ask the question. The table in your master class doesn't seem to mention half cousins at all? I also didn't find anything about pedigree collapse there? Apologies if I am missing something, which is very possible? I have the paper trail here, I am just trying to reconcile the number of shared cMs with that, to ensure the evidence is consistent. If the DNA evidence is not consistent with my other evidence, then more research is needed. Thanks, Sue

On average half cousins share half as much DNA as full cousins (similarly for cousins once removed).

However, you need to bear in mind that the average figures shown in the chart are much higher than the theoretical figures shown in the table - this is because the figures in the chart have been calculated using cousins who are DNA matches, and ignore cousins who don't have identifiable shared DNA. You can see from the table in the Masterclass that only 71% of 4th cousins and 32% of 5th cousins are DNA matches (so about 50% of 4th cousins cone removed). These percentages are probably lower now that Ancestry have raised their lower limit from 6cM to 8cM.

Pedigree collapse simply means that you're related to some of your cousins in multiple ways, so you can calculate the theoretical shared DNA by adding together the figures for each relationship. But when you do this take the figures from the table, not the chart.

It is very unlikely that you will be able to confirm that you are related to someone in two different ways simply by looking at the amount of DNA you share. Instead you'll need to collaborate with cousins to confirm each relationship separately.

 

[Sue_3]

On average half cousins share half as much DNA as full cousins (similarly for cousins once removed).

However, you need to bear in mind that the average figures shown in the chart are much higher than the theoretical figures shown in the table - this is because the figures in the chart have been calculated using cousins who are DNA matches, and ignore cousins who don't have identifiable shared DNA. You can see from the table in the Masterclass that only 71% of 4th cousins and 32% of 5th cousins are DNA matches (so about 50% of 4th cousins cone removed). These percentages are probably lower now that Ancestry have raised their lower limit from 6cM to 8cM.

Pedigree collapse simply means that you're related to some of your cousins in multiple ways, so you can calculate the theoretical shared DNA by adding together the figures for each relationship. But when you do this take the figures from the table, not the chart.

It is very unlikely that you will be able to confirm that you are related to someone in two different ways simply by looking at the amount of DNA you share. Instead you'll need to collaborate with cousins to confirm each relationship separately.

Thanks, that confirms my suspicion that I do need to pay more attention to the maths than I'd like to. I can do stuff with numbers and have several qualifications to prove it, but I don't like them! As for the collaboration, that is something I do like, but isn't always easy or even possible. I've been busy with other things today and will be out for much of tomorrow, but will consider this more fully as soon as I can.

 

[Sue_3]

OK, after reviewing all of the advice the conclusion I have come to is that it is quite possible that my distant cousin and I would share 62 cM. It would be possible if we were just fourth cousins, although the match would be on the high side. Given that we are related in several ways because of the pedigree collapse in the family tree, it is more likely that we would share that much DNA.

I agree that this does not 'prove' how we are related. Just for starters, the range of likelihood in the DNA statistics is too great to predict anything with certainty, or even with a huge amount of probability. It is also perfectly possible that one of us has an incorrect understanding of our family tree, either because the records have misled us in to following the wrong ancestral line or because those records are obscuring one or more 'NPE's (non parental event or not parent expected, depending on whose definition you prefer - either way it means that someone's parent or parents are not those identified in the records seen).

However, my question was 'is it likely' that we would share this much DNA, if the trees are correct: is the DNA evidence consistent with the other evidence? I think the answer is yes, the DNA match does not rule out the relationship that the other evidence predicts.

I will be looking for closer shared matches to give me more confidence that the trees are correct.

 

[peter]

I'd still recommend collaborating with cousins to tease out the answers - the relationships you're talking about are sufficiently distant that there must be quite a few cousins who share one or the other line.

Please note that I'm not talking about shared matches.

 

[Sue_3]

I'd still recommend collaborating with cousins to tease out the answers - the relationships you're talking about are sufficiently distant that there must be quite a few cousins who share one or the other line.

Please note that I'm not talking about shared matches.

I get you, but I've yet to find any 'lost cousins' for anyone in this branch of my tree. I'll have a look to see if I can add a few more of them as ancestors, following my most recent research. The whole branch is 'tentative' because I do not know for certain who someone's father was, and need DNA evidence to help with that. The one living cousin I have managed to track down has agreed to take a DNA test to see if we can confirm that we are related in the way I suspect we are, however they haven't got around to it yet. I know that they are really busy and I don't want to hassle them too much in case they change their mind.

 

[peter]

The one living cousin I have managed to track down has agreed to take a DNA test to see if we can confirm that we are related in the way I suspect we are, however they haven't got around to it yet. I know that they are really busy and I don't want to hassle them too much in case they change their mind.

It only takes 2 minutes to take a DNA test - they can't be that busy, surely?

 

[Sue_3]

It only takes 2 minutes to take a DNA test - they can't be that busy, surely?

I offered to send them the test kit that I already had, but they wanted to organise it all themselves, for reasons that I understand. As well as having a very demanding job they have been dealing with a recent bereavement. I am happy to wait until they have more time and space.

 

[Sue_3]

I offered to send them the test kit that I already had, but they wanted to organise it all themselves, for reasons that I understand. As well as having a very demanding job they have been dealing with a recent bereavement. I am happy to wait until they have more time and space.

Just thought you might like to know that after I drew their attention to a recent Ancestry DNA discount (relevant to their country and mentioned in the LC newsletter) the living cousin did get around to taking a test and the results have answered many questions (and raised a few new ones, as ever).