I had to giggle a little when I read your note because I have also undergone that journey ;-)
One thing is for certain: what we think we know today won't be the same as what we think we know tomorrow!
Most likely there are numerous persons on your twig, they just haven't taken the plunge into DNA testing. You are a pioneer into your sub-tree, which surely contains fabulous undiscovered mysteries.
Hopefully those mysteries will be made clear during our lifetimes.
@Jill Whitehead, Please see my next comment. If the Hammer report is correct, then there are some G persons who come from a Cohanic tradition.
@Stephen Weinstein: You raise some interesting points. For purposes of clarity I usually refer to Cohanim and y-chromosome Aharons as being two distinct categories. Your explanation makes clear that not all y-chromosome Aharons are Cohanim, strictly speaking under Halakhic law. But one needs to be careful here because strictly speaking under Halakhic law, there can be no non-y-chromosome Aharons who are Cohanim, and yet there are apparently many R-M269 Cohanim (according to the Hammer report). I believe there has to be a Rabbinical interpretation of the definition of Cohanim to include also persons who by tradition have become Cohanim, but do not express Aharon's y-chromosome. The purpose of all of this is not to exclude some Cohanim who are not descended from y-chromosome Aharon from the priesthood but to explain and accept how the necessities of how random human reproduction sometimes require cultural adjustment to our ways of thinking.
What I find fascinating about today's discussion landscape is that it is becoming evident that certain parts of the Old Testament are more than postdictional metaphor; certain parts seem to be revealing actual geneaological and social facts which can be merged with DNA, linguistic, and archaeological evidence to build a fuller picture of human history and Jewish history.
Kudos to you and to everyone working in this field!
Have a Splendid Day,