Searching for double cousins

Is there a report, Gramplet, tool or something that can find double cousins? Or maybe even triple cousins? I found a case today where two of my fourth cousins married. They were second cousins to each other. Their children should be double cousins to me.

I though I found some way to do that a while back, but now I cannot remember it.

Gramps 5.1.3 on Fedora 32

Bill Gee

Sounds like the Related Relatives Gramplet

Dashboard view, right click the main screen and select Add a gramplet from the list of installed (visible) Gramplets.

That heads in the right direction, but does not answer my question: Who are my double cousins?

Also, I do not see a way to limit the depth search in RelatedRelatives. In my tree it reports on relationships between ninth cousins. That is only mildly interesting. First and second cousins - yeah, that is interesting, but ninth cousins … Not so much.

Perhaps you had built a custom filter with a combination of rules?

Duplicate ancestors of

Matches people that are ancestors twice or more of a specified person

People with a common ancestor with match

This rule matches people who have common ancestors with someone who is matched by the specified filter. The specified filter name should be selected from the menu.

People with a common ancestor with

This rule matches people who have common ancestors with the specified person.

Hi Brian -

Hmmm… That seems more likely, but still not quite what I am looking for. The “Duplicate ancestors of” filter pulls up a lot of stuff but does not tell me anything about how that relationship was found.

I seem to remember getting output that looks very much like Deep Connections. When I ran Deep Connections on a few of the people that Duplicate Ancestors pulled up, I just got multiple copies of the same chain.

Also - Are cousins - strictly speaking - ancestors? I don’t think they are because there is almost never a descendant blood line from them to me. I share ancestors with cousins, but that does not mean my cousins are also my ancestors.

Perhaps the filter is something that finds people who share more than one ancestor with me? Sort of like “People with a common ancestor with” except it only returns when there is more than one common ancestor.

Best tool for what you are looking for are an external network graph software like Gephi, Cytoscape, Tulip, Constellation or similar…
There are some job to get an exported file into any of those software as it is now, but to be able to find all those connections you need a software that can give you algorithms for “shortest path”, “nearest neighbors” and also be able to show you multiple leaps at the same time…

as a tip if you need it asap: Legacy familytree has some functions that will give you some of the answer if you care to use a windows software other than Gramps.

It might be that you can manage to create some kind of custom search filter for it, if you do, please share it, because I have looked for that functionality for a very long time, researching Norwegians where cousins often got married, as well as brothers married wifes of dead brothers and so on…

Wow, that sounds complicated. Way beyond my modest skills! And far more effort than I am willing to put in.

I might look at search filters. I need to learn more about them, and this might be the excuse that gets me started.

Yes, at the moment it is kind of complicated to get data to use in other software out of Gramps, but some times there are few other options without a lot of workaround that only do half the work…

The software themselves are not that difficult to use, but it is the job getting the data converted to a usable format that is difficult… I have asked for it, but don’t think anyone that have the knowledge to create an export have any interest in doing it.

It shouldn’t be a problem to get data like that in a graphical view or text report, but someone with knowledge need to create the view…

But, now you know that it is possible in other type of software…

Hope you figure out the filter rules needed :slight_smile:

@bgee, do you have a particular definition of “double cousin” that you are working with? The first step before creating any filters or trying any other solution would be to define it as precisely as possible.

Would the following example from my family tree be considered a double cousin relationship? I have a cousin on my father’s side who married a cousin on my mother’s side. Those two cousins were unrelated to each other prior to their marriage. But their children are related to me as cousins in two different ways (having different common ancestors, rather than multiple paths to the same common ancestors).

I was thinking it might be useful if there were a filter rule in the Families view that identified families in which the father and mother were related (other than as spouses), but that would not help in my example.

As a working definition, see Wikipedia:

There are probably other ways to define “double cousin”.

My question was triggered when I discovered a marriage between two of my fourth-cousins. That might not be a good case because they were second cousins to each other, sharing a common ancestor who was also one of my ancestors. A better case in my tree is a set of families where two brothers and their half-brother married three sisters. The families were not related to each other, but both appear in my ancestry.

The report I remember seeing (and cannot find again) came several months ago when I was looking at my relationship to Catherine Howard and Anne Boleyn, two of Henry VIII’s wives. They were cousins to each other, and both are first cousin sixteen times removed to me. I remember seeing multiple cousin paths to Catherine. Those relations were anything from twelve to sixteen times removed.

I wonder if it came from Deep Connections run multiple times? Most times when I click the “Continue” button on Deep Connections, it just gives me the same sequence again. Is there a way to run Deep Connections continuously until it runs out of paths?

It’s a “dirty” hack but at line 237 of

        if self.default_person.handle != active_person.handle:
            self.append_text(_("Paused.\nPress Continue to search for additional relations.\n"))
            yield False

replace with

        if self.default_person.handle != active_person.handle:
            #self.append_text(_("Paused.\nPress Continue to search for additional relations.\n"))
            yield True

This removes the instruction to “Continue” and forces the the loop to actually continue.

On a side issue with the Gramplet, I tested it on my maternal grandparents whom I happened to know were also more than Husband and Wife.

The problem, it returned Husband and Wife based upon each of their children.

It also returns duplicate relationships based upon the siblings of the active person.


Dangerous hack! To remove the Continue, the Gramplet needs a Cancel button that is monitored. (A lot of the add-on features neglect to periodically check for Cancel… or pop a dialog saying that the action cannot be interrupted.)

Without some way to interrupt, an auto-continue could create a near-endless loop if the Tree has a significant amount of Pedigree Collapse,

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I tried the modification suggested below. It does, indeed, make Deep Connections run through all possible paths without pausing.

In the few examples I tried, it turned out to be not much use. Taking Catherine Howard as an example, Deep Connections found a path for Catherine herself, and also for each of her siblings and parents. Although each is a different path by the strict rules, I don’t think they are either interesting or useful. In every case the entire path is identical except for one person at the beginning.

I’ll try to write a report that checks for double cousins in the database. I also have some cases of them in my database.

I too did not understand the need for the added paths through siblings and children. This would only make sense if the sibling or child were anything else but a Birth relative; i.e. if they were adopted and the paths were through the individual’s non adoptive family.

I normally do not use this tool so do not feel the need to file a bug report.

Deep Connections became massively slower in 5.1.3 release.

I have a couple problems with it. It seems to do a shortest path analysis without weighting. Connection through marriage has the same weight as a genetic connection. And a sibling connection is unfairly weighted.

A paternal aunt married her 4th cousin 2x removed (up) and this throws the analysis for a loop. (Literally!)

I have to remove him from the Tree to make the Gramplet work with shared relatives in that branch.

I created a new text report which lists double first cousins in the database. The code checks for persons with known parents and grandparents, then checks for each combination if the two people have different parents but the same four grandparents. I hope it is useful.

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Nice! Thanks! I ran this across my database of just over 9500 people. It found 242 cases of double cousins. That seems high, though as I examine the list I find that most of them come from the same dozen or so families. There are lots of Quakers in my background, with some very large and intertwined families.

Run time was about 30 or 40 seconds, which I think is excellent given the processing that has to happen.

Since is looking only at first cousins, an obvious extension would be to look for double second/third/Nth cousins.

I did a quick look for duplicates and did not notice any. Does the code know how to leave out duplicates? Does it know, for example, that “Doe, John & Jones, Fred” is the same match as “Jones, Fred & Doe, John”? Only one of those needs to be reported.

Other suggestions: An option to set the display format of the name. That is present in most other reports so should be easy to add. An option to set how the list is sorted, if it is sorted at all.


Thanks! I ran it too but it seems not to find everything. May be I don’t use it as needed but I can’t see nothing to do before running it.

I’ve that couple (Pedigree collapse, implexe in french) which seems to me to be relevant to that report but I can’t find it in the report:



Is there something to do to find them in the report?

Yes much more than my database. I have only 20 cases.

I’ll add double second cousins and also try for higher degrees, but I think those get very very rare.

Yes it should avoid duplicates, but let me know if you find any duplicates.

Both are good ideas. I’ll add them. :smile:

Your couple (green) is not double first cousin, since the parents are from three different families, while double cousins are only from two families and pedigree collapse is not checked in this report.