Absolutely love this thread. I have two to add.
Mine and DH's uncles and aunts have the same names. E.g. His uncle is a Fred married to a Betty and his aunt a Jenny married to a Paul and so are mine!
When I was in school, I had a teacher who was from the same small town about 50 miles away as my DMs family. We realised this after I borrowed a pen from him which had his DFs business on it.
Fast forward a few years, I'm in my last year at uni but in London for the day looking at postgrads. Had a really rough year as DGF (DM's DF) recently diagnosed with terminal illness. Nearly didn't go down to London that day but DM convinced me.
Sat waiting at Euston for my delayed train home and hear a voice calling my name, it's teacher from a few years ago! He has moved schools back to his home town and was convinced that I'd been on his train that morning to London even though id come from a completely different city. He was so convinced that he'd gone up to this girl and said hello to her thinking she was me.
We start chatting and he ends up offering me a job at his new school, 10 mins from my grandparents. Go into school a week later to fill in forms and visit my GF for the last time before he passes a few days later. My new job means that I can visit GN twice a week and do her shopping in her time of need. Left just as she moved over to be closer to us purely coincidentally as well!