u/Endisbefore

Recently got a DNA match sharing around 1,600 cM (~23%) across around 90 segments, and the site is suggesting relationships like half brother or uncle. But a few things about it seem off to me.

Our longest shared segment is only in the high 60s cM range, which feels lower than I’d expect for something like a straightforward half-sibling relationship. He comes up as fully maternal side for me, but apparently I show up connected to both maternal and paternal sides for him.

I also started looking through his tree and noticed repeating surnames within his family multiple times, so there definitely seems to be some pedigree collapse/endogamy involved somewhere.

What makes this even messier is that my great-grandfather moved into that area as a governor/mayor type role with his three kids, got the kids to marry locals and later married a local woman before being appointed someplace else himself as well, Because of that, I can easily imagine multiple lines reconnecting over generations without anyone really realizing it.

Now I’m wondering if the total shared cM could be inflated because we’re related through several different lines at once, where my lineage became the local genes and the local genes became my lineage in parallel rather than this actually being something as close as half sibling.

Has anyone here had matches where the total cM strongly suggested a very close relationship, but the segment structure and side assignments didn’t really fit cleanly? I’m especially curious how people account for pedigree collapse/endogamy when trying to interpret shared cM numbers.

Recently got a DNA match sharing around 1,600 cM (~23%) across around 90 segments, and the site is suggesting relationships like half brother or uncle. But a few things about it seem off to me.

Our longest shared segment is only in the high 60s cM range, which feels lower than I’d expect for something like a straightforward half-sibling relationship. He comes up as fully maternal side for me, but apparently I show up connected to both maternal and paternal sides for him.

I also started looking through his tree and noticed repeating surnames within his family multiple times, so there definitely seems to be some pedigree collapse/endogamy involved somewhere.

What makes this even messier is that my great-grandfather moved into that area as a governor/mayor type role with his three kids, got the kids to marry locals and later married a local woman before being appointed someplace else himself as well, Because of that, I can easily imagine multiple lines reconnecting over generations without anyone really realizing it.

Now I’m wondering if the total shared cM could be inflated because we’re related through several different lines at once, where my lineage became the local genes and the local genes became my lineage in parallel rather than this actually being something as close as half sibling.

Has anyone here had matches where the total cM strongly suggested a very close relationship, but the segment structure and side assignments didn’t really fit cleanly? I’m especially curious how people account for pedigree collapse/endogamy when trying to interpret shared cM numbers.