Thursday, 25 February 2016

I only have 126 fifth great-grandparents!

OK, I know that does not seem all that exciting. After all, these people lived over 200 years ago so how important can it be?

Two of my 4X great-grandparents, John Shepheard (1768-1845) and Jane Treby Shepheard (1769-1851), were first cousins who married each other (29 July 1791). Their fathers were brothers so that chopped the number of my 5X great-grandparents by 2, my 6X great-grandparents by 4, my 7X great-grandparents by 8, and so on. This example is not terribly surprising as there are cases in almost every family where cousins marry, shortening the overall family tree. It is just more obvious when they share the same surname. I have found one other case in my family in the same area although it does not deal with people in my direct line.
Marriage record for John Shepheard and Jane Treby Shepheard, Cornwood parish, Devon
In a recent blog post, James Tanner refers to this situation as pedigree collapse. He goes on to say, “[i]n families that come from a rather limited geographic area, it is entirely possible that everyone in the entire area is somehow related and that shared pedigrees are the rule rather than the exception.” What is surprising in the case of my family is that these great-grandparents did come from quite a small parish, Cornwood, in southwest Devon, England but I have found, so far, few examples of cousins marrying in any family. Mind you, while I have transcribed every baptism, marriage and burial in the parish registers back to 1685, I have not done a full analysis of all of the families who lived there. Perhaps there are more examples in the area than I think there are. As far as I can determine, in my direct family line this is the only example of cousins marrying.

What must have been interesting back in the late 18th century in this family is that the children of John and Jane had two fewer great-grandparents which really changed their ancestral line. I am sure it did not matter to these children since all of the great-grandparents were dead before either of them were born.

The children of John and Jane, though, including my 3X great-grandfather, John Shepheard (1792-1870), only had 96 5X great-grandparents, when they normally might have had 128 (25% fewer). The pedigree collapse seems more real when considering these individuals. Do you suppose they talked about their grandfathers being brothers or did they really care at that stage of their lives? Over time, generations can make up ground and the collapse does not appear to be all that great. In my case the difference at the 5X great-grandparent stages is only two people, or 1.56%. It’s hard to get your head around that many grandparents of a generation that far back.

It is interesting when you find close relatives marrying – I consider first cousins pretty close. You have to think, in a small parish like Cornwood they knew each other very well growing up, probably went to school together, attended church with their families together and generally socialized so it was, in the end, just natural that an attraction would develop. John and Jane were married for 54 years until his death in 1845. They lived the entire time within a mile or so of where they had been born and very near most of their children and grandchildren. It must have been quite a love story.
Gravestone for John and Jane Treby Shepheard, Cornwood, Devon
Wayne Shepheard is a volunteer with the Online Parish Clerk program in England, handling four parishes in Devon, England. He has published a number of articles about various aspects of genealogy and is the Editor of Relatively Speaking, the quarterly journal of the Alberta Genealogical Society. Wayne also provides genealogical consulting services through his business, Family History Facilitated.


  1. You should have 128 fifth great-grandparents and 256 6th great-grandparents without pedigree collapse.

    Are you saying you know only 130 of your sixth great-grandparents but 4 of them are duplicates, so you have only 126?

  2. You are right, Randy. I read the wrong line on my table when I typed it all out. It is two less at 5X and four less at 6X great-grandparents. Post corrected. Thanks.

  3. Hi Wayne, I have only found one instance of inter-marrying in my direct line of Hortons from Cornwood - my gggrandparents William Alexander Horton & Margaret Northmore Hillson were distant cousins - their lines intersect back at my 6th great grandparents, Haly Horton (1715-1779) & Mary Maddock (1720-1760). I'm not sure what sort of cousins that makes them - I never could work that sort of thing out! They must have known of the connection though, as Margaret's mother was a Horton & very much alive at the time of the marriage in 1868. As you know the Hortons were all over Cornwood in the 1800s & they were all descended from a Haly (who seems to have moved to the area sometime before his death in 1689) & Mary Trobridge.

    1. Hi Kim. Yes it is surprising that in the small parish of Cornwood we don't see more intra-family marriages. I understand how difficult it can be to figure out relationships, especially when you get past second cousins. In my Legacy program I can set relationships for any individual and then the rest of the people in my tree show how they are related to that person. I did it for my 4X great-grandfather, John Shepheard, and his wife, Jane Treby Shepheard, was immediately shown as his first cousin, not his wife.