Too good to be true?

[Norfolk Nan]

By a sheer fluke I found a strange DNA match - we're an 11cM match according to Ancestry, 3rd cousin level on the paternal side apparently. But according to our respective trees we match way down in the 9th cousins level in my mother's side.  It seems too far back for dna matching but I can't see any link to my dad's side or earlier to either side.  Is this remotely possible and a freeky result or totally impossible?

[PaulineJ]

ive got matches at that kind of level where the paper trail is one parent, but the dna says its on the other side , and a lot closer! (and nowhere were we able to see where).

[Norfolk Nan]

Thank you, it's reassuring to know that it's either right or we are both wrong

[Biggles50]

I have DNA matches of 6cM and two @ 7cM in my Family Tree.

There is BMD documentation for each one linking us together.

So yes low cM matches are not always false positives but they do require a document trail to satistfy myself.

[Glen in Tinsel Kni]

I created a floating branch for each individual in two groups of mystery matches totalling around 140 people and traced between 110-120 of them back to two ancestral couples, so now just two (massive) floating branches. The branches are so wide and deep my tree has gone from 1,500 to almost 9,000 and in a couple of cases stretch 9 generations from the match back to the ancestral couple, if only I could work out where I fit in!

[brigidmac]

I think.it is possible.

  My nephew matches some people who are 5th cousins of his grandmother

But I'm also looking at a bunch of matches to my mothers 4 x ggmother
Who seem.to have larger than normal.cm amounts to our 3 generations including cousins & I'm wondering if ia daughter is brought up.as a sister along the lines so.we are actually a generation closer .

[David Nicoll]

Hi,

   As others have said, entirely possible, bear in mind that direct and indirect pedigree collapse can do strange things to cM matching.
   I have said elsewhere, here. I have a match who shares twice as many cM as their parents. I happens that there is shared ancestry in the 1700’s. You need a deep and wide tree to understand this though.
   The march is through a wandering path in Central Scotland, so not even a particularly small population.
   Like others here I have large dangling match pools, in the US mostly in my case, but at either end as it were, they are matches to both my parents.
   It a small world!

[Norfolk Nan]

I have another tiny match that is about 10cMs and an 8th cousin which I cling to as the only link to a particular line so yes, it happens. The FH software described this latest match as 9c6r and that just seemed so obscure when you read that every generation halves the DNA pool.  And Ancestry says a paternal match and it's definitely not! 

On the one hand there are hard and fast rules about how DNA is shared and I read a warning this week that we're unlikely to get proven links beyond the 4c level.  Clearly that's not true.  And clearly some genes are stronger little blighters than others as I've got several lines without any proven DNA links and others with quite obscure DNA connections. 

[Biggles50]

By a sheer fluke I found a strange DNA match - we're an 11cM match according to Ancestry, 3rd cousin level on the paternal side apparently. But according to our respective trees we match way down in the 9th cousins level in my mother's side.  It seems too far back for dna matching but I can't see any link to my dad's side or earlier to either side.  Is this remotely possible and a freeky result or totally impossible?

In this case I would be very sceptical of the match and you share a MRCA so far in the past, 9th C’s share 8xGGP’s.

I would be looking at a link a bit closer, DNP Painter shows only a 7% probability of a 3C at 11cM when the Mean value for a 3C is 73cM.  Looking at the Probabilities listing a relationship in the 4 or 5C level may be more likely but the trouble is if it is a result of a casual relationship documentation is very unlikely.

I have written this before as there is an unknown 3xGGF in a tree, no likely DNA matches show but one does put a family member of a DNA match in the next village 2 miles away in the right timeframe, means, motive & opportunity he is the prime candidate but there is no documentation other than a census record.