I have a match of 30cM with someone who shares my 5X great grandparents. We both knew that was very high so looked at other names in our lines and found at least three that matched so the direct link could be far back with additions of other families dna.
Well I just looked and I can see that I share 14cm with this match. My mother, who's line he is from, shares only 11cm with him.
I'm quite confused. Surely the dna that matches with him comes from my mother so she would have to pass me the dna. Unless some of the ways she connects with him is in parts that weren't tested? Or does this indicate that he matches with me on my father's side too or that there's a cross over somewhere between his line and me?
The difference may be to do with Ancestry's Timber algorithm. If you click the cM number, it will show the unweighted number, which may well find is the same between you and your mother. The Timber algorithm is rather contentious, as many feel it wrongly reduces some matches by a significant amount, but it also does so randomly, so can reduce the same segment by quite different amounts in closely related people. It can even create a situation where a small match is hidden completely, below the lowest 8cM threshold for matches to show.
Timber was created for homogenous populations like Ashkenazi Jews, Amish, small island populations or other small ethnic or religious groups to reduce their matching numbers, as without it they have many many more than most people as they descend from a relatively small group of people who have intermarried many times over many generations and so people within the group share more and larger segments than most average people would within a larger ethnic group or country.
