Realistically Cadence wouldn't have been around when Celestia and Luna were young, the biggesting reaosn being the fact that Cadence is Celestia's niece and show as a teenager when Twilight was a foal and then an adult... which clearly suggests Cadence was born recentally.
Oh yes, i do. Even if Cadance never was in the same age as the other two. How old is even Luna? Over one millennium? And Cadance, the youngest of the three is going to marry. Fascinating, isn’t it?