not sure you'd class this as coincidence or a bit woo.
I am into genealogy. Many years ago, I posted a query about a census entry on Genes Reunited and a guy replied with some helpful info.
He mentioned there was a chap with the same surname living in his (very small) village and wondered whether we were related. I didn't know about that branch of the family but researched it & yes - we are second cousins. Up till that point I had no idea I had any living relations in that part of the world.
A year or two later we went to a fairly large, busy, country fair in that area. I was in one of the tents and turned round to see an old chap standing behind me. I just KNEW. I said, are you XX and he said, yes, who's asking.
He knew my gt grandfather & my gt uncle so we had a lovely chat about families.