65/67 marker match

[Rebec1951]

I'm trying to make sense of my DNA results. I sent two YDNA samples to FTDNA for 67 markers to see if a family I've researched through traditional genealogy methods is related to mine.

One sample is my brother's, the other is a man whose line I have researched and connected to mine through census and other records. I think his gggrandfather, Alexander, whose brother was John, was uncle to my great grandfather, James Alexander, and raised him from a small child. What I can't prove through traditional sources is that James Alexander was the son of John.

My brother matched 65 of 67 markers of the second sample and is considered a genetic distance 2. Both samples have the surname Williams. The relationship on paper connects at the fifth generation.

Even though I can't connect the two families on paper, can I still be assured that we are related at the fifth generation?

[Frederator]

Unfortunately, no.

DNA mutations are random. So even though the the rates used by TMRCA calculators are the result of tens of thousands of father/son sample observations, and are relatively reliable, each individual dna donor's case will be unique.

The TMRCA calculator takes all that carefully sifted data into account when it tells you the probability that two samples are related a given number of generations ago, but it can only be a probability and never an absolute certainty.

People who are in this game long enough, and lucky enough to get a number of high resolution matches will see some prettty weird stuff from time to time. Like the dude who is GD 5 at 67 with a fellow he shares a MRCA at 1750 but yet at the same time is a perfect 67/67 match with another guy with whom there is no possible MRCA after 1600. Startling results like this seem to be rare, but they do happen.

So unfortunately there is currently no way to answer your question with clinic certainty. On the other hand, good on you for getting such a good match! Maybe additional luck on the paper trail will verify precisely how you two are related.

. . . . Even though I can't connect the two families on paper, can I still be assured that we are related at the fifth generation?

[Rebec1951]

65/67 marker match

Thanks for the response. I am still looking for a paper trail but have been searching about 15 years and the sources are getting fewer.
I neglected to say that the 65/67 match was the only match at that level so far for either of the two samples I submitted. There have been several thousand exact matches at the 12 and 25 marker levels but my brother's sample was the only one that consistently matched all the way up with only the two mutations.

I'm still a bit confused about all of the terms and such. Would a deep clade test provide any further information?

Thank you again for responding to my question.

[rucksack]

As an example, my 4th cousin once removed is a 64/67 match with me.

Our common ancestor was born in 1787.

I think you have an excellent match.

Good luck on the rest of the paper trail.

[rivergirl]

Thanks for the response. I am still looking for a paper trail but have been searching about 15 years and the sources are getting fewer.
I neglected to say that the 65/67 match was the only match at that level so far for either of the two samples I submitted. There have been several thousand exact matches at the 12 and 25 marker levels but my brother's sample was the only one that consistently matched all the way up with only the two mutations.

I'm still a bit confused about all of the terms and such. Would a deep clade test provide any further information?

Thank you again for responding to my question.

Congratulations on the match.
I think it is reasonable to say the two men are related, but DNA will never be able to tell you who or when exactly the connection was.
If all your paper genealogy points to the two men being related, the 65/67 practically match confirms it.

A Deep SNP will not tell you anything else in this case. It is more for deep ancestry, it will not tell you who the common ancestor was.

[Rebec1951]

65/67 marker match

Thank you all for your responses. I appreciate the comments. One reason I did the DNA was to affirm my theory about the two families. Now that I have the matches I will dig deeper to see if I can prove it on paper.