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Why Don't These Cousins Share DNA? | Genetic Genealogy Explained
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- Опубликовано: 8 авг 2024
- Do you look at DNA matches and wonder why they don't relate as they should? This video walks you through one case study.
🤔 Why Doesn't a DNA Match Match Any Other Relatives? 👉🏼 • Why Doesn't a DNA Matc...
This example comes from our viewer, Cosmic Slice. If you would like to submit your confusing DNA match questions, send them to www.familyhistoryfanatics.com...
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Chapters
0:00 Introduction
1:21 Draw Out The Relationships
6:40 Theory One
9:19 Theory Two
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🤔 Why Doesn't a DNA Match Match Any Other Relatives? 👉🏼ruclips.net/video/UkDtca20dUs/видео.html
appreciate your videos - pretty new to these explanations of genealogy. the question i am left with from lack of knowledge: @11:00 when you show f-m as must having shared dna why can't decendent s-m, as 2nd cousin once removed, be part of the group who do not share dna (%5 who do not as shown @7:30 vs 95% who do). seemingly that would also be a plausible explanation of why s-m do not share dna. Again, assuming there is a reason why you did not list that as a possibility.
Isn't there a simpler solution? That her great grand-aunt (A) is her great grand-aunt through marriage, and that S's great-grandfather was the brother-in-law of (A)? Therefore there is no shared DNA between (C) and S's great-grandfather. If that is right, then S and B share DNA, B and M share DNA, but S and M do not share DNA. It's easy to assume that S and (A) are related given that she specifically mentions her great grand-aunt, not her great grand-uncle, but S does not explicitly state that (A) was the sister of her great grandfather. Anyway, just another possibility.
Very good explanation. Myself and 3 siblings have tested and we don't all match the same (3rd, 4th, etc) cousins although we have the same parents. It all depends on which "cards" we each got from our parent's "DNA deck of cards".
That's exactly how this works. If there are 20 genes for eye color, say, you and your siblings could be dealt similar hands of 10 "cards*, but you might not have *any* similar cards.
Thank you for the explanation, it clears up some mysteries in my family. I also like how you drew it out.
I'm glad you liked the drawing out of the problem. I find visualizing the details helps me and others make sense of the situation.
As always, interesting and helpful. Thanks! I read through the comments (always interesting as well) and since I'm nearly always in the State of Confusion (occasionally I'm in Ohio), I can relate to some of the confusion. At least for me, one thing that helps with many vids where I'm trying to keep up w/what's on the screen and process it too, is, slowing the vid speed down to .75 (25% slower) or .5 (50% slower). Just click on the cog wheel/Settings in the lower right part of the video area, choose Playback Speed and select an option. It can help in not missing a key point (like 1/2 relatives weren't considered because the family info given was they were "Full" rels), or maybe catching something I would have otherwise missed and go back and listen again.
In some cases where I want to record a concept, one way is to click the 3 dots at the far right of the menu options (next to Save), choose "Show Transcript" (not always available) and a (usually) pretty good automatic transcription of the presentation with video timestamps pops up on the right. You can turn the timestamps off if you want (unless you want that reference point) by clicking on the three vertical dots to the right of "Transcript" and next to the "X" for closing that window. Then click on "Toggle Timestamps" which will turn them off or back on. Then you can select and copy the particular bit of text you want and paste it in your fav word processor. I find it helpful to have snippets from diff videos on same/similar subject in a doc to review. Ooops, way past time to stop nattering away...🤐
My older brother and I are the only 2 siblings out of 5 who have taken a DNA test. We don’t share the exact DNA either. We do show the same areas of ancestry but his shows more Irish than I do and visa versa on mine! We have sooooo many first cousins though because our parents siblings married siblings within the 2 families, ie, mom’s siblings marred into dad’s siblings!
Excellent presentation - very useful 🙏
Glad it was helpful!
Very interesting video.
I have several unknown DNA matches who are in groups. I believe not knowing who my paternal great grandfather is/was doesn't help me. I get easily confused by all this to be honest but can clearly see writing it down should make it easier.
Thank you
One assumption you are making that I would not based on my tree is that A and C are both full siblings to the ancestor of F and S. I have many half-sibling relationships especially further back on the tree when more women died in childbirth
I'm not making an assumption of full siblings, I'm using the information provided by the viewer. She gave me the information and I spoke to that end. In RUclips videos, one has to work with the information provided by the viewers. Additionally, when asked about whether A, B, and C are full blooded siblings, she confirmed it with other research. Thus, the analysis stands.
Had she had any doubts of relationships, then we could tackle the half-sibling potentiality.
When I cover too many caveats in the video, people get confused. Notice how others have comment that this rather simple explanation confused them.
Just rewatched your video and had another thought. The great grand aunt through which M is linked could be a half great grand aunt (an NPE occurred) and so the amount F, S, and was it B match M would be reduced to the point where not matching is very possible. Just thought I'd add this as I've been rewatching some of your videos to reaffirm your thoughts on the lottery that is DNA inheritance. Hope all is ok with you and the family we you've disappeared from making videos, thoughts and prayers are with you if something has happened, and hope to see some more videos again sometime in the future!!!
I loved how you "DNA detected" it out! Interesting! Cool how you drew it out, what program do you use to draw it? Thank you 😊
For this video, I drew it out in Google Slides to make it pretty. But, you can draw it out using pen and paper or any other chart making tool.
Very good presentation. I have a DNA match on Ancestry with a second cousin but do not have a match with her half-sister, and both have the same mother but different fathers. I would think that I would have a match with both. Am I wrong?
Because of how DNA is passed down, it’s interesting how you can quite often share more DNA with more distant cousins than with cousins of closer genealogical relationships.
For example, I have a 3rd cousin 2x removed on my mother’s side I share 134 cM with (very unlikely, but it happened) while on my father’s side I have a 2nd cousin 1x removed I only share 130 cM with.
Yes, and this is a large source of confusion for many.
I feel like it’s the wording of the question more than the scenario itself
Could you explain further in a new comment thread. I'm not sure what you are saying with so brief a statement. I could respond in so many ways.
BTW... the reason I ask for a new comment thread is because once I respond to you here, YT hides your responses back to me. I would really like to know what your follow-up comment is, so if you could start a new comment stream, that would be great.
Thanks for another interesting video. My guess was that the great-grandaunt C is the half sister to Cosmic Slice's great-grandpa. Wouldn't half relationships have a higher probability of not matching than their full relationship counterparts?
We have a bit of this no-matching business going on between my bio father, me, and my uncle and at least one match. Uncle J matches the lady at 118cM. Neither I nor my father match her. Her great-grandmother is sister to the grandfather of a match that my father, uncle, and I all share DNA with. Uncle J matches the grandson at 157cM, Father matches him at 114cM, and I match the grandson at 60cM. The match that Father and I don't match matches the grandson at 108cM. She and the grandson are 2C1R to each other.
If the relationship to me, Father, and Uncle is as suspected (and hoping to prove!), then she should be 3C to my father and uncle and 3C1R to me, so it makes sense that Father and I don't match her and Uncle J just got lucky in the skittle toss. If it is as suspected between Father, Uncle J, and the grandson, their relationship should be half 1C1R because the match's grandfather should be their great-grandfather, but they have a different grandmother/great-grandmother.
The potential common ancestor with the grandson has the same surname as was listed on my great-grandmother's cemetery record as her maiden name and that grandson match's grandpa lived only 4 or 5 households away from my newborn great-grandmother in the 1900 census. Here's hoping this mystery is well on the way to being solved. If only something like this would come along for my Maggie Robinson Williams!
All of this is fascinating to me. The randomness of DNA inheritance keeps it a long way from ever being boring!
There's a lot of BS and S&M going on in this video!!! Using A, B, C, and D might have been better!!! Great video though!!!
You know... I did use A B C D. Then F for father and S for son. Perhaps E should have worked for M?
Where are you getting these probabilities of DNA sharing between relatives? While going through my DNA matches I have been wondering what the likely hood is of sharing DNA with certain relatives.
23andMe and Family Tree DNA have both put these probabilities on their websites (although their numbers are slightly different). For relationships inbetween what was published, I interpolate.
okay, follow-up question. What if the great grandparent, A and C have a half-relationship there? Would that make some changes to the assumptions?
It would affect the likelihood of the matches sharing DNA (because they'd be 3rd half cousins not 3rd cousins) and because a half sibling only gets half their DNA from one of the parents and they don't share as much DNA was they would it both parents were in common (I hope that makes sense). I'm not sure how much the percentage goes down but I'd expect quite a dramatic reduction from if they were 3rd cousins. I would suspect in the case presented in the video that the match that isn't fully defined is say 3rd cousin 2x removed or further, as the further distant the match the higher the chance of not inheriting matching DNA as it's a bit of a lottery each generation you to down as to whether that email amount of DNA gets passed down and whether it some is passed down it is over the threshold for a match to be confirmed.
Great question. If A&C are half-relatives, then the situation becomes different and we would need a new drawing and theories to test. We would make that drawing, run the tests, and see what would happen like we did in the video.
Since half-relatives share less DNA than the full siblings that Cosmic Slice mentioned, then the analysis would go in a different direction. That would be a topic for a different video or Q&A response.
Same happen to my mom, she did not match a 3rd cousin, but her full DNA sister did.
It's more common than we realize.
How are you doing Lady?
goated page. subbed . love geneology
Awe. Thanks
I have never met any of my great grandaunts or great granduncle. At least not one that's biological. My great grandmother dose have a half sister that took an ancestry test. She shared 4% of my DNA. This is about as close as I'm going to get to having a great grandparent take this test. So me and my brother great grandchildren might not share any DNA do I have this right?
Let me recommend a playlist about inheritance that will lay the foundation for your question. If you will watch those and still have questions, ask in those videos so I can see where you are in the education journey. ruclips.net/video/-f7VUPmgy2U/видео.html
I want to make sure you're not skipping any steps in knowledge.
I’ve run into this issue in my own family tree.
A first cousin of my late father began very extensive genealogical research back in pre-Internet days and subsequently published his findings online. Cousin Dick’s feet-on-the-pavement research involved a fairly insular community (not going into details due to privacy) where he was able to visit the local/regional churches, graveyards, etc. to get his info.
The adopted mother of a young woman who, according to Cousin Dick’s genealogy, is my fourth cousin once removed contacted me to ask about my own Ancestry tree, which thanks to Cousin Dick is also quite extensive. On paper, this young woman is my cousin - but we are not DNA matches, although she is a match to other people on that branch of the extended family tree. Her mother and I discussed it via Ancestry messages, and while it’s possible Cousin Dick’s research was flawed, I think it more likely that our common ancestors’ DNA didn’t make it to one of us.
The further back you go, the more likely that is the case. We only share DNA with 50% of our 4th cousins and 15% of our 5th cousins.
Help us out .. my brother in law does not know who his dad is his mom took it to the grave… he did a ancestry dna test and it turns out his aunt on his moms side is related to him on both sides match… maternally and paternally.. wouldt that mean his mother is related to his dad since her sister is a full blooded sister and related…. So does this mean his mom and dad are cousins ?????
My 2nd cousin once removed shares 232 cM with me, over double expected. His daughter isn’t a match although she does match others in the family.
Similar here.
My 4th Cousin shares DNA but her father & his brother doesn't. No half sister & brothers in the family. To have a 4th I should have the 3rd cousin
i have a question, is it possible to have first cousins only share 6% dna
Yes, that would be on the low end of what is expected.
Please help me better understand "once removed"
The folks at MyHeritage have a great article that explains this well. Check it out. education.myheritage.com/article/how-many-times-removed-untangling-distant-family-relationships/
There is a slight flaw in your logic when you say that if F shares no DNA with M, then S can't share any DNA with M. What if S's mother shares DNA with M through a peripheral relative?? (I'm not proud to say this, but some of my 3rd-5th cousins at 23andme are definitely related to me on both sides!)
I wouldn't call that a flaw in his logic. You're bringing in additional information that would mean S didn't tell the whole story. I have some of that in my parents' families as well
@@williamowens5542 He said "can't," an absolute assertion not supported by the variables.
A good explanation of relationships but no answer for the query. 10% or 5% chance of not sharing DNA is very small. People divulging their approximate age on their DNA accounts is so helpful to figuring this kind of thing out. The telling question is HOW MUCH DNA is shared by B and M? Then how much F shares with B? This should provide a solution.
How are you doing Sharon?
How is it statistically possible that any relatives share not DNA, given that there are so many, many genes to be shared or not shared between any parent and child or between any pair of siblings?
Or are genes inherited not individually from one parent or the other, but in large clumps of genes?
There are approximately 22,000 genes (2 copies of each for 44,000 total). So if they were inherited complete, it stands to reason that you could inherit them from 44,000 individuals. It doesn't take that many generations to have more than 44,000 ancestors.
@@FamilyHistoryFanatics "
Family History Fanatics
21 hours ago
There are approximately 22,000 genes (2 copies of each for 44,000 total). So if they were inherited complete, it stands to reason that you could inherit them from 44,000 individuals. It doesn't take that many generations to have more than 44,000 ancestors."
It would take ten generations to have about a thousand ancestors -- that's way more than we're talking about here. So it appears that we don't inherit genes individually from parents by large sequences of genes. (I think that's how paleontologists can tell how far back a Neandertal ancestor was.) So I guess the question is -- into how many strips, typically, are the parents' DNA broken into for recombination?
I hate to tell you this, but there is another possibility (well there are a few, but I'm assuming everything with the tree and the parentage of the people are all as you expected, otherwise we are getting into tin hat territory), but there could be either a glitch in the DNA test or the database the data is stored in and the matching process. I have my grandfather's DNA matching him, and correctly to a half nephew and his children. There are a few distant matches of my grandfather that match the children but not the half nephew, which is impossible (it can't be endogamy either, the only other way it could be explained as the half nephew emigrated and married someone from the place he moved to, plus her family isn't from where he was from, so this can't be the case). I would love you, or anyone else to explain this. I'd love to know if anyone else has had this appear in their match list. It doesn't happen often, but it does happen.
Don't hate to tell me things that you're considering. That's where the discussion happens, and more teaching can go through.
For close matches, 1st - 2nd cousins, there is a rare chance of a glitch in the program. However, since these individuals share so many centimorgans, the glitches become less relevant than with more distantly related individuals who frequently share small amounts of DNA.
Regarding your situation. Let me consider whether this would make a great video, Live Q&A question, or comment. Then I'll explain what I can.
Should 1/2 second cousins share DNA ? This is my scenario. My Great-grandfather Friedrich was married twice. His oldest daughter Clara (b.1859) was born to his first wife who died. My Great-grandfather married a second time and my grandmother Irene (b.1888) was born to his second wife. We grew up without any knowledge of my grandmother's older 1/2 siblings but I discovered them while researching the family tree. I've connected with Clara's Great-Grand-daughters and they were very surprised to find out about our relationship. I am content to accept that they are related to me but they are skeptical about the relationship because we don't share DNA. Coincidentally they look similar too, laugh like and sound like my grandmother.
Because of the age difference between Clara and Irene (29 years) Clara's grandson and my father were close in age. I have found photos of my father and their father together at family gatherings.
I have DNA matches with descendants of Friedrich's brother and sister so I am pretty certain I am descended from Friedrich. Because of documentation I feel confident I am related to these 1/2 2nd cousins 1x removed but they aren't. Am I right not to stress over the lack of DNA connection or are they right to be skeptical?
I don't have any first cousins on my Father's side of the family because he was an only child. I do have a few DNA tested paternal 2nd cousins and I have a few 4th to 4th plus once removed paternal cousins. So here is my example of a few of my known 2nd through 4th+1once removed cousins.
My Great-Great-Grandfather, who I'll label HAE (the H is for his dad) and his brother, who I'll label as HLE each have great-great to great-great-great-grandchildren. HAE has 3 great-great-great-grandsons (each with a different set of parents); me, I'll call me SE, GE, and GH. SE and GE and direct paternal line descendants of HAE. GH's grandmother is a sister of SE's and GE's grandfathers.
HLE has a paternal line great-great-grandson, KE and a great-great-great-granddaughter, GS (she is a descendant of one of HLE's daughters).
When I compare at-DNA results on Ancestry I find:
SE, GH, KE, and GS all share some at-DNA.
SE GH, GE, and GS all share some at-DNA.
KE and GE do not share any autosomal DNA
Question: Can it be assumed that if all of the cousins above were to have at-DNA tested by any or all of the other major companies doing at-DNA that I would see the same results or could the matches vary by company?
PS: KE and I (SE) have had the Big Y 700 testing done by FTDNA and we share the same terminal SNP/Haplogroup (and I have no reason to believe that GE wouldn't also share that same SNP/Haplogroup).
😕 confusing
Very confusing.
Where did you get confused? I can't explain away confusion without questions to answer. However, if you reply to this comment thread, RUclips hides your response from me since I'll respond right now. So, start a new comment thread with your questions and let's see where you got confused.
I don’t share DNA with my 1C1R (Danny).He shares proper DNA with my Grandmother and my cousins. I share 1170cM with my Grandmother. He shares 890 with her. He also correctly matches my 1C and her daughter (his aunt and cousin). To help solve the mystery I had my father tested. My father has 100% Parent/Child relationship w/my grandmother and me. Father shares 360cM with my 1C1R. Been trying to solve for months. Exhausted. My father also has a 310 cM match that I don’t match. -I’ve checked hidden matches on all accounts including 1C1R.
How are you doing Melissa?
Lance in Cowtown
Thanks for watching.
The Great NorthWest
Awesome. Glad you could join us
Does this mean that 3rd Cousins do not share any DNA?
No. It just means that with 3rd cousins there’s no guarantee of sharing DNA. Only about a 90% chance because you only share DNA with roughly 90% of all your 3rd cousins. So if cousins aren’t matching, they’re probably the equivalent of 3rd cousins or more distantly related.
What Jordan said
I share DNA with 5th cousins and I'm pretty sure that up to about 5 generations it is possible to share DNA.