While there are those that feel that the X Chromosome matches are not too useful, I respectfully disagree. It can be helpful in certain situations. Females who share a Dad will share a full X chromosome(the copy that their PGM gave their Dad) In my case, it was a bit different. I'm not sure why I checked to see if I had any new large X matches at GEDmatch Friday, but i did. It was a rather large match around 34.3 centiMorgans. So I marked it as PGM since it was also in common on my Paternal Phased Kit. This match who is a Male also shared some Autosomal DNA. So I checked and his match was along a segment that I share with about 10 other groups. I say groups because there are about 25 individuals who share this segment which match me in a range from about 18 cMs to 22 cMs. I have never been able to identify which of my lines it came from although I was able to narrow it as coming from my PGM side because my sister and I don't match along this Paternal segment. Dad gave her a segment from our PGF on this portion. With the new information from the X Match, I could further narrow down the possibilities among the PGM lines. Looking at my lines I narrowed mine down to Frizzell, Kennedy, Knox, Sutton or Weaver. This new match had no pedigree at GEDmatch or FTDNA and only the name and location of his Surname in the Ancestral Surname section at FTDNA. I sent him a short email listing the possible surname connections and mentioning Tennessee as a possible area of connection and also mentioning that the large X match would indicate that our match is from his maternal lines.. I heard back the next morning. He didn't know much about his Mom's lines but he did give me the name of his grandfather. To my surprise when I checked on that...it led to the grandfather's Mother's maiden name---Sutton. But how did these Suttons connect to mine? They were in Bedford County Tennessee which was the area where mine had lived. I traced them back to about the mid 1800s and then things start looking really familiar. I share a set of 3rd Gr Grandparents with his Mom and we also share a Morrow line as a sibling of my direct Morrow line married downstream into his Suttons.
That match had been at FTDNA for six months. I hadn't noticed the new match at FTDNA because the automal match segment is not terribly great and so it was pretty much buried there by those who match me at larger amounts. I never would have noticed it had I not checked the X matches at GEDmatch. I also would not have likely noticed it at all had he tested at AncestryDNA. Sure the smaller segment might have shown up in my Distant Cousins matches which I don't check much. I'm almost certain that if you match someone exclusively on the X and no other chromosome you can only see that without great effort(and on some sites maybe not at all) but you can at GEDmatch. At least using the interfaces at the site. You might notice if you download and use a spreadsheet to manage your matches. I think at FTDNA you would really have to dig thru the matches. At AncestryDNA I don't think you would even see it because if I remember this correctly the algorithm that AncestryDNA uses to generate your list of matches doesn't consider the X. If I am wrong on that, someone please correct me in the comments
I've got a good deal of the Bedford Co TN books in my personal library so I'm going to be going thru the land and court records looking for additional information.