Comment on loving sisters. by Maiko-of-Harmony

I have a question: How did they earn their titles?
You can't say Nightmare and Dreamcaster are royalty because they aren't even real, their Twilight's dreams...
I noticed OC alicorns need a rank Therefore all my alicorns have been banished to be either pegasi or unicorns ;-; Except Dreamcaster and Nightmare. Da end.
Please do tell me how they earned their titles though