Confused by X match

[LizzieL]

I tested a couple of years ago with Ancestry and uploaded raw data to several other sites including FT-DNA, which as well as autosomal matches shows X matches. Looking at some X matches of identified cousins, I have one which looks as if it is impossible. This person and I are half 3rd cousins once removed, so we have only one shared ancestor rather than two. But that ancestor is through my paternal grandfather, from whom I could not possibly have inherited any X DNA. I have looked into the possibility of a second connection but that doesn't seem to be a possibility. Her great grandfather was born in Berkshire and emigrated to Canada. His wife and her parents were born in Canada, I haven't traced back further but from surnames I expect they were from Scotland. For the next two generations the two ladies who married into the family, one was of French descent and the other was of Irish. No connection at all with any other Berkshire families.
I have similarly ruled out any connection with my mother's side because there are no names or locations in common.

Any suggestions how I could have this X match with this lady?

[LizzieL]

I have used the chart referenced on this post

https://www.rootschat.com/forum/index.php?topic=790473.msg6463194#msg6463194

and highlighted the common ancestor of both my match and me. It seems impossible for both of us

[familydar]

You match on PART of the x chromosome and this can happen by coincidence

[LizzieL]

You match on PART of the x chromosome and this can happen by coincidence

Thank you.
I have found she is also Gedmatch and checked the match between us on X Chromosome. It is two quite small segments, 5.2 cM and 3.8 cM.
I will see if any of my other X matches on FT-DNA are also on Gedmatch.

[LizzieL]

I have another person (male) who is shown as X match by FT-DNA, and again should not match as our common line starts from his father and paternal grandfather. Gedmatch shows no match on x chromosome, which is as expected. So I am very sceptical about FT-DNA results. And if some could be coincidence as in first match, then it doesn't seem a very useful DNA tool.

[LizzieL]

My first match (M) has following matches on 23

Chr   B37 Start Pos'n   B37 End Pos'n   cM   
23   32,101,060   32,956,232   5.2   
23   141,416,813   142,961,967   3.8   

Her first cousin (J) -female- is also on Gedmatch. I match her on 4 segments although they are also small

Chr   B37 Start Pos'n   B37 End Pos'n   cM   
23   47,945,021   52,067,217   4   
23   124,288,056   128,268,623   3.6   
23   144,982,975   146,621,314   3.4   
23   150,982,525   152,834,467   4.2   

Their fathers are brothers, so had a 50% chance of inheriting the same X chromosome from their common mother.

No segments in common between me and the two ladies.

But comparing them with each other

Chr   B37 Start Pos'n   B37 End Pos'n   cM
23   2,700,157           38,615,759   61.2   
23   46,941,458   50,581,326   4.5   
23   96,425,266   154,916,845   86.3   

More than 50% match