Recently we (two full sisters and a full brother) think we may have found a half brother who is 50 years old on Ancestry DNA, where he is being categorized as Close Family-First Cousin.

  • sister 52yr share 1,902 cM over 60 seg 100% match
  • sister 51yr share 1,833 cM over 61 seg 100% match
  • brother 50yr share 1,316 cM over 50 seg 68% match

Each of the above can be g-parent, g-child, uncle, nephew, 1/2 sibling.

Also a ****nephew 14yr share 975 cM over 36 seg 99% match**** can be 1st cousin, gg-parent, gg-cousin, great uncle, grand nephew, 1/2 nephew, 1/2 uncle

Given these results is he my half sibling?

I ask because his biological mother is saying our father (deceased would have been 79) is not his biological father.

I really do not know much about all this DNA but I think the answer is simple and I just want confirmation from a reliable source.


Assuming that this suspected half sibling is of the same generation as you (which his age suggests), and because the shared cM for each of you and your full siblings with him falls "within" the range (1317 – 2312, mean 1783) suggested by The Shared cM Project 3.0 tool v4 for half siblings, I think it likely that he is a half sibling to you.


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