My introduction to the blues was through my dad's old 78s, not country blues, but more old time jazz. I recall Dad singing St. James Infirmary and songs, that while not strictly 12 bar stuff, were very bluesy sounding.
The "great folk scare", as Utah Philips called it, peaked my interest in country blues and I had the opportunity to see players like sonny & Brownie, Skip James, Rev Gary Davis, Mississippi John Hurt, R.L. Burnside, Muddy Waters, Bucka White, Yank Rachell, Carl Martin, Geoff Muldaur, John Hammond, John Mayall ...live in concert. I also searched out and found many recordings by blues artists that I'd read about or heard mentioned by performers that I admired. Nowadays you can find almost anyone on Youtube, but it ook some real sleuthing in the sixties.

What is (are?) The Blues? I'd rather not try to come up with a definition.
There is the basic, 3 chord 12 bar progression, which probably everyone will call the blues, whether it's happy or sad.
Some folks vary the chord progression slightly, adding a VI7th chord in the 8th bar and a II7th chord in the 9th bar.
Jazzier blues players will add more chord substitutions, sometimes two or more chords per measure, but retain the twelve bar pattern.
Jimmie Rodgers added 4 bars of yodelling to the end of the 12 bar pattern, but it was still very bluesy.
There are also songs like Key To The Highway, which keep the bluesy feel even though they're only eight bars long, and Nobody Knows You When You're Down And Out or Hank's I'm So Lonesome I Could Cry which have a bluesy feel too.
I don't agree with Hoot's allegation that white men/women can't sing the blues. If it sounds good, it is good.