Mine is a lot closer to the present than most. It's sad and kind of weird:
My mom grew up on in a small town on the coast of New England, the kind of place that population doubles during the summer when the tourists come in. Her family became very good friends with one of these "summer" families; they owned a bunch of the seasonal beach cottages and lived about 2.5 hours away in the same state so they visited the coastal town much more frequently. My mom and one of the summer family's daughters really hit it off and became best friends. The two families remain very close and by the time my brother and I are born, we are all one very big ("unofficial") family.
Unfortunately, small coastal towns in the 1950s and 1960s didn't have a lot to offer the young people who were born and raised there. My mom married her HS sweetheart. He had joined the military and after the wedding they moved to housing on the base he was stationed at which was 1,900 miles away from home, hot, humid, and flat as hell.
A few years later, my mom and her first husband divorce. Mom stays in the flat state for awhile but eventually goes back home to her parents' house.
Around this same time (I think), mom's best friend's younger sister died. (I asked my mom a few times when I was a kid what the story was but she never wanted to talk about it other than so say "Little sister had always been ill." I ordered her DC recently and cause of death was complications from pneumonia.) She was 22. Little Sister had also married her HS sweetheart and when she died they had only been married 6 months.
This is where my personal knowledge of events gets a little fuzzy. I don't know whether my mom met Little Sister's BF/husband before she moved to the flat state (which might be possible but he lived/was from where LS and family was from, not where my mom's family lived) or after she returned home. Either way, about a year and a half after LS's death, my mom and LS's husband (widower?) got married. And about 3.5 years after that they had me.
So, if each of my parents' first marriages hadn't ended and if they didn't have the mutual friendship/connection through mom's best friend I wouldn't be here.