if my great great grandparents are 1st cousins does that mean I can check farther back on my cousins other line?

Question

My great great grandfather John Martinussen married his 1st cousin Karen Maria Ostness and I suspect I might also be related to their granddaughter's father as well through a different line. This is due to my cousins father maternal line having the name spelled exact way and it being a fairly rare name with multiple spellings. I have checked up to the 1800's and found them living far away from each other and it's far enough back that probably wouldn't be able to test unless being related on another line helps. This cousin is in her 90's and I have no idea if she is living or not and or if she has any descendants. there is no one to do a Y test or Mitochondrial since in both of our lines it goes through a male ancestor and then a female. and I don't know any cousins on that side that are not descended from the same female so I wouldn't even know if her brothers have any living descendants. the earliest point it could is probably about late 1700s since I traced up until mid 1800's on both. 

Answer 1

I always, (or try to anyway), research in-laws and extended family, because it seems, given enough time, a lot of them seem to loop in and out of the family tree. For example, my first cousin, Robert Simerly, daughter of my dad's sister, I had always thought that was the only blood connection between us, but, just out of curiosity, I researched his father's line too, and what do you know? One of his great-grandfathers was also mine. I find that is common, especially generations and decades ago, when people often married other locals and would stay in the same locality for decades.

Answer 2

Cousin marriages will move you up one generation genetically, but not genealogically.  My 6th great grandparents were 1st cousins, normally the children of m 6th great grandparents would be 7th cousins, but because they were 1st cousins, there children would be my 6th cousins, and the children of 6th cousins would be my 5th cousins (genealogically 6th cousins), and so on down the line, to the point were my genealogical 5th great grandparents would normally have children who would be my 6th cousins, actually would have children who would be my genetic 4th cousins.

On my fathers mother side, I have a 3rd great grandmother who was the daughter of double first cousins and that really tilts the genetic table.

Answer 3

I think you may be hampered a bit.  Let's say that you and your cousin are 3rd Cousins 1x removed. You can track the DNA segments up to but not including John Martinussen and Karen Maria Ostness. 

Normally, you would need to match a known 4th cousin on his side and one on hers to support being full cousins. The problem is that this 4th cousin is a blood relative of both John and Karren.  John and Karen's parents are siblings.You would not be able to detect a Non-Parental Event.  

For John, the best you could do is to find two males that have John or his ancestor as a common ancestor who match using ySTR. There are even some caveats that should be noted with this approach.

The problem with using mtDNA for either John or Karen is that as 1st cousins, they may have the same mtDNA.  This would be true if John and Karen's parents are sisters. I believe there may be some other concerns as well.

I hope this was not too confusing...

Comments

the line I am trying to see if it connects is through her paternal grandmother  so no relation to Karen or John since those are her mothers parents which are John and Karen. Also I don't known if any of any of Johns sons had and sons or just daughters I know Herman for sure only has a daughter I could try maybe looking into some of his other sons I didn't add for lack of proof they existed other then somebody has a picture of all his children  of course I could look in to the other sons that I have proof. However I know all of great grandmothers (daughter of John and Karen) descendants have in person contact it's through her brothers daughter nobody actually talks to her other sisters children so no way of contacting his sons descendants to do a y dna.

---

I am not sure what you mean by "trying to see if it connects through her paternal line". It seems that you are concerned about some non-traditional connections.

You might consider running the Gedmatch report..."Are your parents related?

I am not exactly sure who has had their DNA tested. Are you looking at who to test and what tests will help you?

---

no my parents aren't related I just happen to have ancestor with same surname as her paternal grandmother that is several generations back and was wondering if that cousin marriage on her mothers side would help check if it's coincidence and the ancestor is several generations back so probably to far for autosomal dna and there is no possiblty of Y  Dna because both of our lines it switches genders to get to that name.