Distinguishing half sibling from niece/nephew using AncestryDNA?

Question

I did the ancestry DNA test and also uploaded my raw data to GEDmatch. I have located two close family matches and I'm wondering how to find out how close we are. Either half siblings or niece/nephew.

TA (male) & I (female) match at 1897 cM with the longest being 195.6 and 49 segments.

RD (female) and I (female) match at 1821 with the longest being 144.7 and 33 segments (we have X-DNA of 196).

We are all adopted and have NO biological information or ties to the biological families. TA and RD have no shared DNA. From what we have read, TA is from the paternal side and RD is from the maternal based on X-DNA -- is that correct?

How can we find out if this is a half sibling or niece/nephew/aunt match?

Answer 1

Unfortunately, there is no reliable way to get the answer to your questions. More frustating is that X-DNA Match may be phantom. I mean that there is a lot of false positive matches around X chromosome. Also genetic tests do know nothing about in what generation are you and your relatives. Thet state only difference between you and others, or how far is the MRCA. So the relation like half-sibling and niece/nephew is totally indistinguishable from each other if you don't use more data like birthdays. But in this case we must take into account that some times uncle can be younger than niece particularly in really big families

The good way of analysis is to try to build the surrogate kit for "parents" of each pairs and try to make cross-analysis or find more matching kits in available databases like GEDMATCH. It may lead to new clues.