Ethnicity estimates are really just an estimate, and in this example, aren’t really relevant.
As you and your mystery match both have matches with cousins on your paternal line, your connection is obviously on that line. It looks like aunt/uncle or half sibling relationship are the most likely.
I suggest testing at least one of your and your matches siblings, which may clarify. Is your father still alive? Even better! Consider testing him, which should give you the answer to the half sibling question.
The more family who test the clearer it is likley to become. Do you have any other close cousins on your father’s side, apart from the one who is a match to you and your mystery match? Test them if possible to clarify any aunt/uncle relationship.
Failing that, look at your father and your matches’ mother’s movements around that time. If you are half siblings, the parents must have met up somewhere. Also look at the movements of your father’s brothers … and the movement of your match’s mother of course.
Does your match have any siblings who have tested? Are they also a match to you?
Just a few suggestions …. I’m sure others will have more.
Good luck and let us know how you get on.
