Pollycat76,
For the past 50 years my father and I could not locate the birth and parents for my Great Grandfather, but had managed to compile an in depth Tree for most other family lines. After both of us undertaking DNA tests a few years ago, I went through the closer matches and allocating the matches to our known family connections. This did involve having to create new family branches to find some of the connections.
This left approximately six/eight closer matches where no connections could be found. We knew the approximate year of my Great Grandfathers birth so started creating new trees for these unknown families and and expanding them to ensure that there were no possible way that GGF could form part of that family.
Eventually, a new tree was formed where one child suddenly ‘vanished’ when they were a late teenager. The date of birth of tied in with my GGF and we found out that he left North Wales and moved down to London, adopted a new Surname and started a new career.
Similarly to the above, I have an adopted Uncle whose birth Mother was known but only a vague surname for his father who allegedly dies in WW2 which passed down via my grandparents.
After having DNA tests done, again I matched up his know maternally family matches and started working through the remainder. This eventually located a family in Canada (with a similar surname, but with different spelling), where I found a member who during WW2 was in the UK and was based approximately 10 miles away from where my Uncles birth mother was working as a nurse. We assume that they must have met up at a dance or similar and my Uncle resulted.
His father did return to Canada (where he was already married with his own family) but we have not made contact with his birth fathers his children/grand children yet, to reveal they have a half brother/ uncle.
So what worked best for me (but obviously may not work in all circumstances) is to remove the known matches and find out the links to the remaining matches.
Good luck,
Al & Al