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Old 12th January 2015, 09:33 PM
GoneResearching GoneResearching is offline
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How is total cM or percentage shared Effected By Being My Own Cousin With Cousins of

I have seen a few Relationship Charts that show the possible avg. percentage of DNA In Common based on how you are related to another person. And I have seen articles talking about likely/possible amount of total avg. cM in common ranges based on specific relationship levels.

BUT has anyone at FamilyTreeDNA or elsewhere figured out how being your own cousin affects those numbers/percentages with cousins of that branch? I assume they would go up but by how much – a little or a lot?

If what I suspect in my lineage is correct …

One set of my fourth great grandparents were first cousins that married so their grandparents (my sixth great grandparents) are the common ancestors making me a seventh cousin to myself. I have found DNA matches to several sixth cousins and a seventh cousin (I think because I’m still waiting to learn the rest of his lineage to figure the exact relation) for this branch of my tree. The common ancestors with the sixth cousins are the parents of my fourth great grandma (who married her first cousin) so I am really double-related to them. I’m their sixth cousin through my fourth great grandmother and seventh cousin through her husband/my fourth great grandfather. How does my double dose of kinship affect the likely avg total cM range or the percentage shared we share? Normally the avg. percentage shared for sixth cousins is listed at 0.0122% or 0.83 cM. Does anyone know how much it could potentially be increased?

Now for the seventh cousin also on this same branch the common ancestors are the sixth great grandparents. In this case I am a seventh cousin to this person through my fourth great grandmother and a seventh cousin through her husband my fourth great grandfather. How does my double dose of kinship affect the likely avg total cM range or the percentage shared we share? Normally the avg. percentage shared for seventh cousins is listed as 0.00305% or 0.21 cM. Does anyone know how much it could potentially be increased?

If the total CM range or the percentage shared is much higher than “normal” with these cousin situations would this add weight to the two first cousins married situation?

Also, if the suspected fourth great grandparents were half-first cousins instead of full-first cousins how would that effect avg. total cM range or percentage shared? In the case of the seventh cousin, I would be a full seventh cousin and a half seventh cousin to that person.

If there is an article about this kind of situation, please point the way to finding it.
I hope someone has an idea of what happens in this type of situation.

Regards
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