Explaining how all DNA matches are shared with Half sibling?


I have DNA matches from Ancestry, FTDNA, GEDMatch, and My Heritage. My half-sister also tested with Ancestry. It confirms we are half siblings and share the same mother. I do not know who my father was, so in my search, I realized that ALL of my DNA matches are shared with my half sister. I was trying to isolate those matches we don't share, in hopes that I could find my father and/or relatives. I am new to genealogy, so I don't know if I am way off in this understanding.

How can this be that all of our matches are connected in some way?

How can I find my father in this case?

There are so many features of GEDMatch that are too complicated and advanced for me.

Connie Nicholson

Posted 2018-11-26T01:33:10.937

Reputation: 11



There are 3 possibilities:

  1. You're reading things wrong. In this case, we need a lot more information to be able to help you sort it out.
  2. This is just your bad luck.
  3. You belong to an endogamous group (Jewish, colonial American, Mennonite, Hawaiian, etc) where it's common to match someone on multiple lines. If this is the case, then you would match a lot of people on both your mother's and father's side. You can rule this one out if your birth parents were of very different ethnic groups.

Cyn says make Monica whole

Posted 2018-11-26T01:33:10.937

Reputation: 2 426

I can second this. I'm an Ashkenazi Jew and almost all my 23andMe matches also match both of my parents. – Ellen Spertus – 2018-11-27T16:46:00.047

Also, they could in fact be full siblings. – RobertShaw – 2018-11-29T18:04:10.010

@RobertShaw only if the OP badly misread the results and the family history is a lie, or if they belong in the small region where both full and half siblings are possible (easy to sort out with a chromosome browser but it's not done automatically). – Cyn says make Monica whole – 2018-11-29T19:14:06.880


If your father was a close relative of your half sibling’s father, that would explain what you are seeing. If, for example, your father was a brother of your half-sibling's father, then you share your entire family tree, from grandparents on back with your half-sibling. If your father was, say, your half-sibling's uncle, then you would share only half of your half-sibling's paternal tree.

Jamie Cox

Posted 2018-11-26T01:33:10.937

Reputation: 861