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FionnSneachta
08-22-2020, 11:42 PM
Someone who matches my mum messaged me today on MyHeritage. His family lives in Brazil but he is of Spanish and Portuguese descent. He shares 42.5 cM over 1 segment on chromosome 15 20004966 - 33719535. There are only two shared matches. ISOGG has it that a single shared segment at greater than 30 cM has a 90% likelihood of a shared ancestor within 6 generations.

If interpreting it right, the ISOGG seems to have 20060763 - 25145260 and 27115823 - 30295750 as IBD regions on chromosome 15 https://isogg.org/wiki/Identical_by_descent
These regions are both included in that 42.5 cM segement but also goes beyond it.

It does look like the match might be an IBD match. They have an extensive tree but MyHeritage does give him 10.5% Irish, Scottish, Welsh.

C J Wyatt III
08-23-2020, 12:20 AM
My understanding is that those are Excess IBD Sharing regions, meaning pile-up's.

I wouldn't waste my time on that possible match.

Jack Wyatt

rober_tce
08-23-2020, 10:59 AM
Possibly, it's a pile-up. Here there is an article about excess IBD shared regions:

http://www.khazaria.com/genetics/excess-ibd-regions.html