Shared 18% DNA

[Tracey2016]

Hi I'm new to all this. I recently done a DNA test and have just received the results. It's showing alot of matches, but a few I'm unsure of or what to make of them. One came back saying we shared 18% DNA on my fathers side another one saying we shared 11% DNA again on my fathers side. I contacted both these people, the one that was 11% said she's never heard of the name I gave her. Strangely enough she is related to the person that shares 18% DNA with me. I haven't a clue who they are, but my father was a only child so how can they be related to me. I also recently found out that my dad's father was married before he met my grandmother. Can anyone share any light on this as I'm totally confused. I have a 2ND cousin on my mothers side who I know and I only share 7% DNA with her.  Tracey

[Jo6100]

My known first cousin shares 13%/ 900 cm with me so you have a close match. It may be that there was a child from the first marriage and neither family know about each other. My husband has a half sister who shares 25% dna/1770 cm so that shows that these are likely first cousins in my view.



Jo

[Tracey2016]

Yea I'm starting to think that hopefully I can dig in a little further

[RJ_Paton]

DNA Painter gives the probable relationships as

18% DNA
69% probability Grandparent Aunt / Uncle Half Sibling Niece / Nephew Grandchild
31% probability
Half Aunt / Uncle † Half Niece / Nephew † Great-Grandparent Great-Aunt / Uncle 1C Great-Niece / Nephew Great-Grandchild

11% DNA
95% probability
Great-Grandparent Great-Aunt / Uncle Half Aunt / Uncle 1C Half Niece / Nephew Great-Niece / Nephew Great-Grandchild
5% probability
Great-Great-Aunt / Uncle † Great-Great-Niece / Nephew † Half Great-Aunt / Uncle † Half Great-Niece / Nephew † Half 1C, 1C1R

depending upon your age and the ages of the matches you should be able to eliminate some of these "probabilities"

[TreeDigger]

With any DNA match you need to find what is called the Most Recent Common Ancestor, or MRCA, from whom you and your match have inherited the bit of DNA you have in common. It could be that bit of DNA is larger in your or the match's case, but it's the overlap that counts.

In the case of matching centimorgans (cM) of 20cM or less, this means you'll have to build your tree and that of the match quite a ways back, including all of the branches. The matching DNA could've come from your paternal grandfather's great-grandmother on his maternal side, or your great-grandmother's great-grandfather on her paternal side. There are many options. It's also possible the MRCA is even further back, or closer.

In any case, it means you have to do some research 

[Biggles50]

18% is about 1224cM which is a close relationship.

With you using percentage that indicates to me that you took a DNA test with My Heritage, please confirm if this is the case?

Without doubt the best company to take a DNA test with is Ancestry, they have a vastly greater database of people who have been tested.  Also a copy of the DNA data can be downloaded from Ancestry and uploaded to My Heritage, ftDNA and Gedcom thus increasing the number of DNA matches.

Now given the close relationship you have I am going to suggest a DNA strategy.

If you have Siblings then get them to take a DNA test.

As you have no known Paternal First Cousins you have no one whose DNA can be used to cross reference.

If you are aware of a Paternal Second Cousin then they to can take a DNA test.

This will maximise the chances of determining relationships.

Meanwhile printout a 5 generation pedigree family tree and with each DNA match that you link to and include in your tree you then mark them on your printed family tree at the MRCA you share with said match.

Once you have added a few DNA matches to the printout it will become clear where there are xGrandparents where there are no DNA shared matches.  Why I am stressing the importance of a chart is to validate that you have proven DNA matches in your tree that link to each line of your Grandparents and to each line of your Great Grandparents.  If you have none then there is an NPE in your tree, if you have these proven matches linked to MPCA’s then your Father may have Fathered a child by another woman, or Grandfather may have, or Grandparents may have given up a child for unofficial adoption.  There are a lot of permutations possible, so do be aware of them.

In a family tree there can be an NPE event, ie “not the parent expected” or Non-Parental Event” despite there being paper evidence it can be totally wrong and an unofficial adoption may have taken place.

Be prepared.

[tatt1994]

Hello Tracey.

The first thing to do is draw up your own family tree.  Putin as much detail as you can so any brothers and sisters you have and your grandparents names, dates of birth and place of birth if you know it. It may be  that one of your ancestors had a child or children you dont know about, possibly from your grandfather's first wife. 

I mainly use ancestry so I dont know much about My Heritage, if that is who you used. There are Facebook pages for people who help solve DNA mysteries, there is one called DNA detectives uk.

[Cell]

Hi Tracy,
How many cMs  do you share with them ? Whether using my heritage  or Ancestry , they both show   cMs  and  %.
Enter the cMs  that you share  with your 18% match into  a dna painter to give a more of a guestimate/ probabilities

To give  you an example of the huge  differences of using  %  instead of the cMs into DNA  painter , my probabilities drastically differ if I use the % that I share with my  known parent's  half sibling  ( who I share  17% with ) rather than our shared  cMs

 Putting  in my shared 17% percentage  in dna painter  gives  me a 32% of  me being their  half sibling or full  Nephew Niece. And 68% of being a half Aunt uncle, half nephew Niece and so on ( and will give me a "prediction" that I  may share  1265cm, I  actually  share 1162cMs )

"68% Great-Grandparent Great-Aunt / Uncle Half Aunt / Uncle 1C Half Niece / Nephew Great-Niece / Nephew Great-Grandchild

32% Grandparent Aunt / Uncle , Half Sibling Niece / Nephew Grandchild"


 Then if I put in my  shared  cMs ( 1162cM)  instead of  my  17 % that I  share ,changes the  predictions/ probabilities percentages by a huge amount- it  is then only 7% that I am a half sibling, full Nephew/Niece and a 93% that my match is my half uncle, full 1st cousin  and so on, and my % will  also change to 15.6 % instead of the 17% that both ancestry and myheritage has given us.


"93% Great-Grandparent Great-Aunt / Uncle Half Aunt / Uncle 1C Half Niece / Nephew Great-Niece / Nephew Great-Grandchild

7% Aunt / Uncle † Niece / Nephew † Grandparent, Half Sibling, Grandchild"

https://dnapainter.com/tools/sharedcmv4

If it were me , I'd  build a tree around them, and if at all possible persuade   your close relatives to test , your siblings  if any, and  if known , second  cousins on your  father's  side.

Very Kind regards .

Ps that's very  high  for a second  cousin  (your known cousin on your mum's side). You say only , "only 7%".  I share with all my  known full second  cousins  4%  (one is 5% but I share over 300 with her unlike my other second cousins who are all in their 200s)
Are you sure you don't  mean that it is   your first cousin once removed ? Ie your parent's first  cousin, or your  first cousins child. I share  that ( 7%)with my first  cousins once removed , as too my child shares that with his  first cousins once removed too .

7% puts  it  very  loosely around 521 cMs which basically there's  only a 3% chance of being second cousins,  totally possible of course, but the odds are really low.

 Only  asking are you sure  ,  because  I know of  quite  a few people in my family  that incorrectly call their 1st cousins once removed their  second cousins,  and 7% seems very  high for 2nd cousins.
Kind regards

[Petros]

On the point about 2nd cousins.
I have 3 2C matches on MyHeritage at 3-5%, respectively 212.5, 334.7 and 316.4 cM and a fourth on FamilyTree DNA at 206 cM.
I have none on Ancestry where a 339 cM match can only be a half 1C