I am looking for a birth father who may or may not be called McGuinness.
Have a maternal half brother who tested, so now can say which side matches are on on gedmatch....but it would seem this family met before a couple of generations between.
The only paternal 3rd cousin match is father unknown..as i found out after i spent months building her tree only to find she used her husband's family in the tree..She won't upload to gedmatch.
I have a mirror tree containing all the paternal matches at 4th cousin stage..looking for a common ancestor.
I can't work it out..spend hours every day..gedmatch is A919901 should you fancy joining in.. 
Child born in mullingar westmeath left Ireland aged 5 now in Midlands Birmingham. Birth mother found years ago now deceased.She gave a name..but who knows.
Any help would be appreciated, a few have tried and given up. It's also uploaded to genesis,DNA land,my heritage and ftdna.
Many thanks
Hi there, I came across this post when researching my surname, McGuinness. You may have already solved this by now but I thought I would reply just in case you had not.
I ran the kit number you refer to above and I just wanted to let you know the results. We matched on 11 shared segments over 8 chromosomes. They are only small segments, the largest being 4.3cM however on the chromosomes where there are several, they add up to 7-9cM. I am aware that people do not believe these small segments to be of any value, however, I disagree. I have found these broken segments useful, in identifying half cousin relationships.
So in saying that, the person you are assisting matches on my Paton/McGuinness line (3x great grandparents). She matches with a confirmed 3rd cousin on the same line.
I have DNA matches on Ancestry with the same surname as your person; and others with the surname in their trees (who are mutual matches with others who are connected with this same line).
I am reviewing the results against the segments in DNA Painter and my initial thoughts are that the connection is closer than 3 x great grandparents and could actually be in my grandfather's generation but I need to look at this further.
Happy to assist if you are still trying to work this one out.
Nikki McGuinness