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View Full Version : Can a child have a larger match with someone than a parent?

Mary from Italy
05-08-23, 22:59
My son's results are in, and Thrulines came through quite quickly, which was useful.

However, it threw up something a bit odd: it showed a common ancestor for my son and one of his matches who I don't have.

It's a small match, only 8 cM, but a genuine one with a good paper trail, and as it's on his English side I obviously have the same common ancestor.

I've checked the match out, and she's showing as no match with me.

I realise that the amount of DNA inherited is random, but is it possible for my son to have a larger amount of DNA shared with a match than me?

He can't be related to her through his father, because my OH's tree is 100% Italian.
Phoenix
06-08-23, 09:17
If you both had seven centimorgans in common with the match, neither of you would show. It could well be the case that your son coincidentally had an additional centimorgan in common from his father.

There are others who know much more than me, but I don't think centimorgans are discrete lumps, but can further be divided.
kiterunner
06-08-23, 09:22
I think you probably both share the same amount of DNA with that person but Ancestry's Timber algorithm has reduced yours to below 8 cM and not your son's. I have lots of matches where it shows me sharing more DNA with them than my Dad does, but when I look at the "unweighted" figures, we both share the same amount.
Mary from Italy
06-08-23, 21:58
Ah, that makes sense, thanks!
Mary from Italy
07-08-23, 19:45
Just found another, where my son has a 44 cM match and I only have 28!

The match has no online tree, and has some shared but non-triangulated matches with people related to me.

No Italian ethnicity, so can't be related to son's father.
kiterunner
07-08-23, 21:43
What does it say when you click to view the unweighted amounts?
Mary from Italy
07-08-23, 23:03
This match is on MyHeritage, so I think the amounts are unweighted, but you're right, I should have checked the segments.

He has 3 small segments in common with my son (under 9 cM) which don't appear on my page.

Then there's a large segment on the same chromosome which is larger in my case than my son's, so it does make sense; they'll just have downgraded the smaller segments in my case.

Thanks!
Glen TK
17-09-23, 09:00
I have quite a few in one line where two consecutive generations have tested, in quite a few cases one generation will have a match the other doesn't and it can be either way.