Hi David Nicoll. Sorry about confusing everyone even myself.
Yes, I was struggling as to how to put those shared DNA results.
so first I used A's match list and that's for A to C and A to D
and then with pro-tools C to D which gave the 309cM over 16 cM
Then I changed it to make C the person with a match list and looked at that list
It did not show A or D. in his list. This was confusing too. That was what I meant in the last two items.
Now I also have a huge task set by Biggles which I will tackle tomorrow But I have more :
I thought i might see what i could fond about A's mother via Ancestry.
Again it's a hind sight endeavour and again I am on the outside looking in and have been told that "it has all been done ,There is no need to do it again' Well! Done by other's than me and I should know better than to accept that.
So I began on A's mother. It has altered quite a few things , all which need seriously checking . But I do probably have the unknown father of C. I also need to check through all the matches as I need to find that surname which I am sure I saw. It's added two more male children and lost the Sister.

Question for anybody : Dose anyone know how and where to find divorce records. C 1961. South Australia Area.
Hi Steve3180, Thank you for your reply. Yes I am pretty certain that the issue of the half brother has resolved. And as above I think I know his father but I need to check that out first. I hope you sort yours out too.
Thank you everyone I will check tomorrow as it's late here, Aussie Land.