At 175cM there are a lot of relationship possibilities but it does have a high probability that it is a Half relationship.
1) Have you mapped out a tree for the 175cM match?
2) The shared 101cM match, are they also in the tree with the 175cM match?
If the answers to 1) & 2) are both yes then what is the relationship between the two?
ProTools most useful feature is seeing how much cM shared matches also share with each other. This info can be used to build them into a family tree as the cM may give a cue to MRCA’s.
In Police drama’s we see, Means, Motive & Opportunity are criteria used in solving the crime and in this case the Brother certainly fits the Bill (sorry bad pun).
You could also check on the various Newspaper sites to see if there was any Paternity Cases reported, unlikely given the adoption but it is stone that needs turning.
Alas it is one of the downsides of DNA is that there is very likely not going to be a paper trail.
If we assume that you have identified the Biological Father then I would look to include all his children and grandchildren in the family tree and I would approach the older ones and after explaining the situation I would ask for their help and offer to give them a DNA test kit.
The latter worked for me.
Yes there is a good tree for the 175 cM match. He has four great uncles all born in the same area, but only one still lived there in 1939 and lived about half a mile away in the next street. I’m assuming he still lived there in 1945.
I agree there is unlikely to be a paper trail, unless the 175 cM match comes back and says “ah, that sounds like great uncle ‘thingummy’. What a rascal he was!”. There definitely isn’t any from the mother’s side, who were surprised she even existed when I told them about the adoption, so it must have been covered up at a very early stage. There is almost no chance of a paternity suit being filed since the mother was already married and according to the adoption record it was agreed that the child would be given up to a family friend – she was actually one of the mother’s first cousins. The adoptive father covered the whole thing up with an elaborate written document explaining that the mother had died in childbirth and her name was unknown, which was certainly untrue.
The 101 cM match was my mistake I’m afraid – she doesn’t have a tree, and unfortunately neither does a 165cM match. However, there are at least three lower cM matches at 39, 24 and 20 to my DIL whose trees all connect into the 175 cM tree, although none of them have DNA matches with Mr 175cM. They do match with the 165 or 101 cM matches to him though. I assume that’s not so surprising at the lower end of the cM matches. The trees join at g-g-g or g-g-g-g grandparent level.
I'm currently working my way though the Protools shared matches to Mr 175cM and putting them in to Excel to see if I can make any sense of it all. Most of the lower matches don't have useable trees, but those that do all join into the 175 cM tree at some point. One thing that does stand out is that none of the shared matches, or any of the shared matches of the shared matches, have any common ancestors with the maternal side of the child.
Does it sound like I'm onto something here? Or is it just wishful thinking?