I wonder if there's like a Pantheon of Alicorns representing things
Celestia is the Princess of the Sun and day
Luna is the Princess of the Moon, Night, and Dreams
Cadance is the Crystal Princess and Princess of Love (apparently[?])
Now let's add another layer. We know an Alicorn can be corrupted into evil because we saw Nightmare Moon. Now look at Chrysalis. Her form is something that closely resembles an alicorn. It's quite possible she was once the original Princess of Love, who got corrupted. Basing on a fanon that she was the Pony who accidentally took the love poison, it's probable that it in turn corrupted her and after a long time it changed her permanently to something she isn't.
Now let's recall how young Cadance looked. She looked like a regular unicorn when twi was young. Could it be possible that she was a normal Pony, unicorn or otherwise, who became worthy to become a Princess herself?
Lastly, King Sombra... Could it be that he was under training to become a Prince as well? And in the process, became corrupted before it came to pass. Could it be that Chrysalis was ALSO the original Crystal Princess? Her name matches pretty closely to crystal eventhough a chrysalis is a cocoon of sorts. After her student, Sombra, fell deeply in love with her, he gave her the love poison and took it himself, which in turn messed with her love related magic, making her crave the love and desire of everypony to just survive. Sombra however felt lost, he loved his princess but his princess wanted everyone else's love and couldn't be satisfied with his. He then became corrupted himself in wishing to rule the Crystal Kingdom as a king, in hopes of attracting the attention of his Queen, Chrysalis.
I'm mostly overthinking a kid's show here, but I love the mythology behind it enough to contemplate these things.