Chevrolet Chevelle El Camino Impala Bel Air Theory

So, as people may know the 70's El Camino and the Chevelle are practically brothers.
But back in the 50's the El Camino was brother to the Bel Air 55, 57 and 1960.
But then in 1963 The Bel Air became the Impala

 

And?

Did I miss something or is this something you could have just said in one of the many car or discussion threads?

 

(imported from here)

 

Infinite minds were blown that night.