maternal haplogroup and X-DNA Comparison: is this likely a relation?

Question

A member of my maternal haplogroup (K1a4) has a nominal 10.5cM at estimated 5 generations match via GEDmatch which suggest the possibility of a distant cousin (A*/Ancestry test compared with T* test). The X-DNA comparison at defaults has all-gray no match result with the output showing below, the image shows significant portions on Chromosome 23 with full, half and no match. The autosomal comparison shows significant match on chromosome 20 (a big blue signal).

What should I adjust in the settings to understand any actual inference of a relationship, or is this not a real/meaningful relation/data point? My objective is to trace my maternal haplogroup K1a4 ideally by name and as specific a location/path as possible (records suggest New Orleans as the last point of reference and before this Denmark and Sweden). I am trying to quantify this specific sample as a relation and then collect more information to find an intersection where/if possible.

• Minimum threshold size to be included in total = 700 SNPs
• Mismatch-bunching Limit = 350 SNPs

• Minimum segment cM to be included in total = 7.0 cM

• Chr 23

• Largest segment = 0.0 cM
• Total of segments > 7 cM = 0.0 cM
• No shared X-DNA segments found

Answer 1

mtDNA and X-DNA mostly are not related.

If two persons share the same mtDNA haplogroup it just means that their common direct maternal ancestor lived ~10000 years ago (when this haplogroup was developed). It means nothing more. Of course, this person may be your sister, for example, or maternal aunt/uncle. But you can prove or disprove it by comparing your and this person's autosomal DNA.

You state that you have DNA overlap of 10.5cM size with this person. It is nothing too, because I have a lot of matches with the same overlap and there is no proved relationship with them. I believe that matches with ~10cM means that one shares with you common ethnicity compound or your ancestors lived in the same region.

Of course, it is always good idea to check your genealogy tree and this person's one as deep as it is possible. But the chances to find common ancestor are relatively low.

Answer 2

A match on maternal haplogroup may indicate a common ancestor on the direct maternal line (mother, mother's mother, mother's grandmother, etc). The inheritance pattern for the X chromosome is more complex. This article explains:

https://dna-explained.com/2017/02/07/using-x-and-mitochondrial-dna-charts-by-charting-companion/

Keep in mind that in the 1800's it was common to have large families and multiple marriages with children, resulting in half-siblings, whose descendents share half as much DNA as full cousins would. In other words, a match with 10.5cM at estimated 5 generations could actually be a half-cousin at 4 generations.