I think this is highly dependent on luck. If you're friendly and happen to live near other, outgoing, friendly families, then the odds of befriending them are higher. It also helps to have a friendly spouse (it helps a LOT).
My best friend for 20 years (we've since fallen out of touch), was someone I met in kindergarten?
How did we become friends?
My surname starts with a "G" and his starts with an "H" so we were seated next to each other
There was a girl who I couldn't stand in high school... but we bumped into each other in a train station on the opposite side of the country... and hung out all afternoon.
Just being from the same small town made an immediate (but brief) connection
It feels corny to say, but you really can't make old friends.