This refers to when two or more people encounter each other in completely coincidental fashion. You might notice your old classmate from three countries away is now your waiter in a place you had no reason to expect them in, and you might say “wow, what a small world”. You might notice two people who you know from completely different spheres miraculously know each other. You might recognize by chance that your penpal has made a cameo at a venue you’re at.
But what was your most profoundly coincidental encounter?
Huh, I looked hard and still don’t get how this is unclear. The “their” isn’t me because it’s third person, and it can’t be the region of South-East Asia or high school guy himself because that doesn’t make sense. That should leave one possibility. Singular their is a thing, if you’re unfamiliar.
I’ll just clarify. My South-East Asian cousin married someone not in the story, and their college roommate, high school guy, was present as a guest, which was highly unexpected. Hilarity ensues.
Ah, singular their.
It’s not that common.
It really is. You’ll never hear “someone forgot their umbrella, I hope he/she comes back for it” in real, native speech. Singular “they” has been around in that context for centuries.
Using it for a specific, know person is new. In this case it’s a specific unknown person, so it’s optional, but I chose to, just because it minimises personal information shared. My cousin in not nonbinary, for what it’s worth.