Double DNA?

[darkerhorse]

My Sicilian grandparents were from the same small town in Sicily, had the same surname, and were 3rd cousins to each other, sharing one set of 2x GGP. Their common 2x GGF carried their surname (also my surname).

Their 2x GGP are my 4x GGP. My understanding is that I'd be expected to inherit about 1.5625% DNA from each 4x GGP, or about 3.125% DNA from the couple.

Because of the duplication, I'm thinking that, in my case, the expected inheritance is doubled: 3.125% from each 4x GGP and 6.25% from the couple. If so, does that mean I've likely inherited more DNA from my surname line than from any other line? Can my percent Italian exceed 50% due to the duplication in 4x GGP? Any other implications?

[mjclayton1]

Nothing against the good folks here (whose breadth of knowledge never ceases to amaze me), but this question might be better suited for DNA-specific forums. Have you tried looking into any of these?

https://isogg.org/wiki/Genetic_genealog ... ook_groups

https://forums.familytreedna.com\

There are many "DNA-heads" that could probably readily answer your question(s). That said, if you do happen to get your answer(s) elsewhere, I would hope that you post them here. I'm curious as well.

[darkerhorse]

I meant to post it here under the Genetics topic.

I suspect someone here will answer, but I'll check out the other websites.

I have relatives also on my surname line whose grandparents were 2nd cousins to each other - same scenario of same surname, same town. That might make them expected to have inherited from their common GGPs twice as much as I cited above for me. I understand those 2nd cousins got permission to marry from a priest in the U.S.

The one who takes the cake are a couple in my grandfather's generation who were 1st cousins to each other - the husband had my surname and the wife had a different surname, but again, same town. Imagine trying to sort out DNA inheritance for their descendants.

[lyn1982]

I suspect on my fathers paternal side his grandparents were 2nd or 3rd cousins - I don't have the tree that far back, but Lipari was very isolated and I noticed cousins on his separate lines matching when they shouldn't.

As for how it effects things - I've got 44 DNA matches descended from

Mario Cannistra
1784–1846

Edit
Francesca Caravella
1784–1846

I suspect I might relate to them in even more than 2 ways.