Consanguinity index calculations?

Started by living Cooley on Sunday, March 31, 2013


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Showing 1-30 of 32 posts
3/31/2013 at 12:31 PM

I think it would be an interesting feature if some sort of consanguinity index calculation could be performed for a given profile's known ancestry. A lot of times, that figure gets underestimated or poorly calculated in royal bloodlines - for example the listed consanguinity index for Franz Karl, Erzherzog von Österreich is stated to be 16.59% @ but given that he has only 393 different ancestors in 10 generations with no unknowns I think that is a significant underestimation of his true consanguinity index. Even outside of royal bloodlines, some type of consanguinity check could prove useful in terms of identifying how much genetic material has been recycled in a given family.

3/31/2013 at 12:50 PM

Just for comparison purposes, Franz Salvator, Erzherzog von Österreich (who married the granddaughter of Franz Karl) is listed with a consanguinity index of 17.48% While it's certainly possible that he has a higher index, it would be interesting to be able to get a more complete comparison between the two of them given the apparent underestimation for Franz Karl.

3/31/2013 at 12:59 PM

Franz Salvator's tree is complete to 7 generations, so I've invited the profile to the Complete ancestors trees project.

3/31/2013 at 1:35 PM

Inviting some more profiles with high consanguinity indexes and tree completeness:
Ferdinand Karl Viktor, Erzherzog von Österreich-Este
Ferdinand IV, granduca di Toscana
and Maria Antonietta di Borbone-Due Sicilie, contessa di Caserta (25.69%)

3/31/2013 at 4:53 PM

Carlos II, rey de España has a very complete tree (already in the project) and also a very high consanguinity index - 26.37% - not surprisingly, since his father married his niece. Even given that, he still has only a few fewer ancestors in 10 generations than Franz Karl.

3/31/2013 at 8:35 PM

Meanwhile, Felipe V el Animoso, rey de España with only a few more ancestors in 10 generations has an index of only 7.76%. In my opinion, the cumulative effects of multiple generations of inbreeding aren't being well accounted for given these wide disparities.

3/31/2013 at 8:38 PM

Yes, having the close intermarriages in the generations directly before makes a difference, but I suspect in all of these cases the percentages are on the low side.

4/1/2013 at 9:47 AM

I'd find a consanguinity index interesting as well...

Private User
4/1/2013 at 10:03 AM

Anyone who can explain what a "consanguinity index" is?

I am working on an app which can show all the paths up to an ancestor and would like to know if "consanguinity index" is something useful that can be implemented as well.

4/1/2013 at 10:27 AM

Well, in non technical terms it's a percentage which indicates how closely inbred a person or animal is, There are a couple of different methods of calculating this, I'll see if I can dig up some of the links I was looking at yesterday. In the meantime, a general reference explanation can be found at

4/1/2013 at 10:58 AM

Finding multiple paths to the same ancestor would definitely be related to consanguinity, though I'm not certain of how useful the index would be in your app

4/1/2013 at 11:13 AM

Different methods for calculating a consanguinity index percentage (or coefficient of inbreeding)

Private User
4/8/2013 at 7:14 AM

There is a little program I have used which can calculate the index for everyone in the database.

4/8/2013 at 4:05 PM

Very interesting, Jadra!

I sooooo try not to feel, in any way, shape or form, responsible for who was "doing" who... the past 2000 years or so. lol! I DO so have other modern views, on the subject, as well... but that said, I STILL find it fascinating... because, the more times the same mix as remixed with an altered version of the same mix, only altered... through, whatever else they DID NOT SHARE.... and to be a living culmination of these STRONGER ATTRIBUTES. Stronger then, due to being doubly... and at times... triply introduced... and multiply co- existent, within each individuals personal Blood I.D. ie. DNA- Code.

4/22/2013 at 4:09 AM

Maria Carolina Augusta Bourbon-Two-Sicilies is an interesting addition to the discussion - her mother's parents were double first cousins and her mother married her uncle. She is listed with a consanguinity index of 22.98%

Private User
4/22/2013 at 4:22 AM

I am running a program and so far she only has 393 diff ancestors (out of possible 2026)

4/22/2013 at 5:34 AM

Princess Frederica Charlotte of Prussia her parents were double first cousins, her maternal grandmother and paternal grandfather's parents were first cousins and the mother of those two siblings' parents were first cousins. According to the peerage her index % is 15.95

4/22/2013 at 5:36 AM

thanks Jadra, very cool to see the wheel version :)

4/22/2013 at 7:40 AM

Prince Adalbert of Bavaria (1886–1970) / Adalbert Prinz von Bayern (1886–1970) His parents were first cousins, his mother's parents were double first cousins and his maternal grandmother's parents were uncle and niece. More consanguinous marrieas further back, of course. Though whether the blood relationships hold true for all of this has been questioned by some.

and they are quite the good looking women.... the two burbons. I´m really, fascinated... in a creepy- sort of way. q:o))

Private User
4/22/2013 at 4:01 PM
details about ancestrs count in a comment bellow the image

1/8/2016 at 11:52 AM

Judy Rice,
Thank you for inviting me to join this project. Because most of my family tree is laced with intermarriage of cousins "Pedigree collapse" is an interest of mine and "implex" is a word that I use daily. I believe that an understanding of pedigree collapse is essential for all genealogists to avoid the illusion that a binary representation, such as the popular image of The World Tree, can accurately depict our real ancestry. I am quite surprised that the concept of pedigree collapse and the calculation of consanguinity index has drawn only 28 comments in this discussion to date and that there has been no comment at all since April of 2013. To nurture people's understanding a starting point might be at the well sourced U.S. Census Bureau's "Historical Estimates of World Population" from 10000 BC to 1950 at or graphs such as the ones at

Private User
1/8/2016 at 2:34 PM

My grt grandfather Chief Pierre Thawenrate(Atawenrate) Rice b 1814 was married three times two of his wives were related to him you know when on their marriage cert dispensation granted by the Archbishop of Montreal it is a wonder i turned out normal

Private User
1/8/2016 at 2:34 PM

My grt grandfather Chief Pierre Thawenrate(Atawenrate) Rice b 1814 was married three times two of his wives were related to him you know when on their marriage cert dispensation granted by the Archbishop of Montreal it is a wonder i turned out normal

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