One is love. Only a few blinks ago in history, surprise was not a variable. I have a photograph of my grandparents at a birthday party, sitting side by side in a tearoom. He is 6 and she 5, with a satin bow and a coy smile that says I know . Today love is often a mystery, a stroke of luck, a happy accident.
Few folks marry the person next door.
They don't know the person next door. They marry the roommate of the cousin of the guy they ran into at that thing. The downside of choice is that you can end up with someone who shares your interests but whose family has none of them. They might as well come from Pluto or West Virginia. You suspect your mate was a foundling left on the doorstep in a Moses basket.