Confirm or Exclude a possible 1/2 Uncle

[mpbeall]

I have AncestryDNA matches with two individuals (who are 1st cousins to each other) that imply they are descendants of my paternal grandfather, but not of my paternal grandmother.

The amount of DNA shared with each suggests we are half-1st cousins once removed – that is, either their common grandfather or their common grandmother was the extramarital child of my paternal grandfather.

What marker level of yDNA test of a patrilineal descendant of their grandfather should be sufficient to exclude or confirm their grandfather as my paternal grandfather’s child? I have taken a FTDNA 67 marker yDNA test.

[prairielad]

yDNA testing can not confirm father son relationship, but it will indicate they share a common paternal line (all males that share their all male paternal line will have a similar yDNA signature)
ie)Grandfathers brothers all male descendants will have the same yDNA as you

That said, minimum yDNA37 recommend, yDNA67 better.

[mpbeall]

yDNA testing can not confirm father son relationship ...

YES, yDNA ALONE cannot confirm a father/son relationship

BUT when atDNA tests of multiple individuals, their matches, their shared marches, or their lack thereof has narrowed the search down to either a single husband or wife being the extramarital child of my paternal grandfather - a close yDNA match between a patrilineal descendant of that husband and myself would certainly suggest the husband was my 1/2 uncle; while a widely divergent match would exclude him, and by default suggest that his wife was my 1/2 aunt.