DNA Testing

If you read what the testing companies write it probably will be confusing. But if you read my series of (so far) 7 articles you will have a much better understanding of what's possible, which test(s) to use, and who should test.

This is not correct (see the articles). Most DNA puzzles can be solved without the involvement of any men, and whether the people who test are from the same generation is irrelevant (normally you'll want samples from the earliest generation on each line).

 

If you list the people who are still alive that could be tested and their probable relation to your great grandfather then it becomes clearer what can be achieved.

There are two main types of test to consider. YDNA tests which as you surmised must be taken by a male from the male line to be tested. Or an autosomal test which can be taken by anyone.

Note if you are going for the YDNA test then it MUST be from an unbroken male line. You indicate that your grandfather was his son and your mother was his granddaughter. Thus the YDNA chain is broken with your mother, so your brother cannot YDNA test to answer your question as they got their YDNA from your fathers side not from your mothers.

You need a brother of your mother, or a son of your mothers brother, or your grandfathers brother or a son of your grandfathers brother. Etc. It MUST be an unbroken male line otherwise you are testing the wrong branch of the family.

For YDNA you can get matches for dozens of generations back. For autosomal DNA matches you can test yourself but as Peter says the closer the person is to your great grandfather the greater the match potential.

Your problem with any test will be you won't have a sample of your great grandfathers to compare against. Since there is a second marriage involved the simplest but pricey way would be to have at least one preferably two or more people, test from each marriage.

If you are limited in the testing to only autosomal testing then you have to eliminate the chunk of DNA inherited from your great grandmother that both sides will likely have in common. If you are lucky enough to have a known male descendant in an all male line from the first marriage and from the second you will be able to compare those results with an all male line from your own family. This lucky situation is rare hence resorting to autosomal testing.

 

IF you are going to use a Y-DNA test then the males need to be descendants in the male line - simply being a male descendant ISN'T sufficient, it needs to be males all the way back. Normally this would mean they both have the same surname as the supposed common ancestor but in this case it's a bit more complicated (name-wise).

However there are relatively few situations in which a Y-DNA test is the best one to choose, when cost and benefit are taken into account, and this may not be one of them. Just because you could use Y-DNA doesn't mean that you should use Y-DNA. Y-DNA tests are significantly more expensive than atDNA tests and they're also limited in what they can tell you.

But then you'll already know all this if you've been reading the DNA articles in my newsletter....