When you are deciding who in your family to DNA test, don't forget the older generation. I did in my post a couple weeks ago. Within minutes of my post Blaine Bettinger and Dave Nicolson illuminated that blind spot. Blaine commented,
If you can't test both parents, of course - I've tested both my parents and thus haven't tested my siblings. There's a few reasons to do so even though, as Tim Janzen points out for phasing purposes, but these are for very advanced phasing purposes.Dave added,
Siblings of your parents are fair game for this same analysis (unless you have THEIR parents tested I have a tested parent, a tested uncle, and an untested parent and aunt... Hoping mom and her sister will be willing to test, to fill out that generation...When recording the information that can illuminate your family history, the autosomal DNA of your family's oldest generation gives the longest view back into your ancestry. I wrote the earlier post with my own personal blinders firmly in place. By the dawn of atDNA testing for the general public in 2010, I was the older generation in my family. To compound my situation. I am an only child and therefore have no siblings to test.
From that perspective I was challenged by Judy Russell and Thomas Jones at RootsTech 2014. Judy very effectively demonstrated how knowledge of our family members can disappear forever within 3 generations unless we care enough to record and preserve it. Dr. Jones likened DNA to the oral histories that too often disappear unrecorded with each of the members of the older generation of our families as they pass on.
So far no one has challenged the math of "Should I Test My Siblings Also?" There is still plenty of time to help me refine my calculations in that post. In the meantime I will throw some more out to you to review.
Testing Parents vs Testing Siblings
Blaine was correct. If you are fortunate enough to have autosomal test reports on both your parents, testing your sibling will only be of minimal value. Also Dave made a very good point about the importance of collecting the autosomal DNA of your uncles and aunts. The recombination of autosomal DNA through the generations quickly begins to make it difficult to trace shared segments back to commons ancestors. Every generation the person being tested is closer to that common ancestor, the more certain we can be about our conclusions.
With yDNA and mtDNA that focus is not lost as quickly as the generations pass. However, it does become more difficult to find the right family member(s) to test to trace some of our lines.