Reminds me a little of my dad's story. He has a half-sister somewhere who was adopted because my nan was 15 and (obviously) unmarried.

I did a DNA test hoping to find answers, and I thought I'd found them - someone with a surname I don't know, with a match in the right range to be a half 1st cousin.

Uploaded my DNA data to GEDMatch, and she showed up there as well.

Except on GEDMatch, we actually have some shared matches, and they're all on my mother's side.

So now there's another adoption, or an affair, or something on that side of the family as well.

Trying to talk my full (known) cousins into taking tests so that I can narrow it down, but they're understandably hesitant