In the middle of last year, a Sydney woman had a DNA test. She received more from it than she had bargained for. At almost the same time, another woman, in Jacksonville, also had a test. Both had been born in London, one in 1947 and the other in 1951, and both had been adopted as babies. What their DNA told them was that they had similar ancestry. In fact, that they were probably half-siblings. The ABC made this great radio documentary about them.
https://www.abc.net.au/radionational/programs/earshot/me,-my-half-sister-and-her-biological-mum/10461548
(Spoiler, it's not a gay story.)