Trying to solve a paternal mystery, making sure I understand Y-DNA/FF results

[sawfish]

I am trying to determine who my maternal great grandfather is. My great grandmother never revealed who fathered her child (born in London, 1921)

There is no documentation to be had - she emigrated to Canada shortly after he was born.

That leaves me with DNA to try and find the identify.

I first did a Y67 test using my Uncle as he is a direct paternal descendant (grandson) of Mr. X. I had good matches at the Y67 level; one genetic distance of 1, two genetic distance of 2, and two genetic distance of 3. All five individuals had the same surname.

So my first question - I think I should be able to safely assume from those 5 matches with the same surname that I have found the surname of Mr. X? I guess the only way he would have a different surname is if he was adopted and ended up with a different surname.

I've tried to use the information from those results (emailing back and forth and some family trees) but haven't been able to find a likely candidate.

I then added the Family Finder thinking I had the surname I just needed to find more matches to come up with the right person.

I've got the FF results back and there are > 1000 total matches but 0 matches with the expected surname. At least one of the Y67 has done a FF but I read in the documentation that this situation can happen, a Y hit but no FF hit, and it likely means the Y match is > 5 generations.

Now to the part I really want to understand - I did an advanced match search to display people that were on both the FF and YDNA result.

I came back with 0 Y67, 0 Y25, and 5 Y12.

So, as I understand it, the five people in the results should at some point have a common male ancestor with my Uncle and each other.

My research at this time would be to trace back the direct paternal line of these 5 people (to the 8th generation if possible) where I should either find my expected surname (from the Y67 results) or at least these 5 people having the same male ancestor at some point.

Am I understanding this properly and can I make these conclusions or is there a problem with my understanding?

Thanks for any guidance - i'm working my way through understanding everything DNA related and it is a lot to take in!

[ech124]

A Y12 match is very common and I would not read too much into that, especially if you are in a popular group such as "R".

1921 is not too remote, so you should be able to rely on the FF test as a good tool. In theory, if the represented tested relatives are random, about 25 percent of the matches should be related to the missing grandfather. Using the FF "in common" tool, perhaps try to define your uncle's matches into clusters. If you have done the FF test yourself, pay the most attention to those FF matches that you and your uncle share.

[hfp43]

sawfish -

Consider uploading a copy of your Family Finder raw data results to GEDmatch. You're likely to find a ton of new matches there. And if you've the resources and the interest, consider an AncestryDNA test as well.

Your close surname matches at Y-67 are a very hot lead.