Will DNA testing solve this query?

[BRO64]

Thanks Ruskie and Maiden Stone for your input.
I think the best way forward is for granddaughter A to take the test and upload it to a site then wait to see if anything materialises from it.If nothing does I think it might be best to put it to one side.
It's a bit frustrating because we're almost 100% certain who the father is.It would be fantastic to know because for one we can follow the true family line.I suppose with the massive stigma attached to such events that happened back in the day it's not surprising that everything was kept close to their chests.
Many thanks again,
BRO64

[Maiden Stone]

I suppose with the massive stigma attached to such events that happened back in the day it's not surprising that everything was kept close to their chests.

As all concerned seem to have been members of the same family, I suggest that stigma may persist.

[BRO64]

Thanks Maiden Stone,
As a parting shot looking at the family tree of the potential father there's a potential 4th couisin of granddaughter A.If by chance that said couisin has uploaded a DNA test,would their results concur with granddaughters A in anyway?

[Mike in Cumbria]

It's a bit frustrating because we're almost 100% certain who the father is.It would be fantastic to know because for one we can follow the true family line

It does, of course, depend what you mean by the true father. Is it the person who provided a germ cell, or is the person who raised the boy,  cared for him throughout his childhood and did all the things that Dads do?

[BRO64]

Ok, I'll rephrase that,
Trying to find the real bloodline.
As regards to raising him ,clothing him etc.what went on is private as you can appreciate,
Enough said.

[Ruskie]

Yes, if any cousins have taken DNA tests granddaughter A should see a match with them.

[Eric Hatfield]

I have quickly drawn up the family tree you have described, and we can see that both these women today have inherited approximately 12.5% of the DNA of the parents of each of the original A & B sisters (their Great Grandparents), and 25% of the DNA of their apparent biological father B (their Grandfather), which makes up half their DNA. The other half of their DNA has come from their other parents and will be different.

But if your scenario is wrong then one of the women won't have the 25% from the male B.

So I think the answer to your question is this. If both these women test, they should have approximately twice as much DNA in common if your suspicion is true, than if your suspicion is false. That should be pretty clear.

I'm not an expert, but that is how it looks to me. Of course that still leaves the human issue of opening up a can of worms, as others have said.

[BRO64]

Thanks once again RUSKIE, your input is much appreciated.
Thanks too Eric,if your explanation is correct it's given me a much clearer picture of the whole scenario.
On a personal note it was sons A wish to find out who his father was but sadly he is no longer with us.
Thanks again.