Board Thread:Questions and Answers/@comment-93.175.79.160-20160905234204/@comment-25942629-20160906213016

Alas, we have yet to receive a clear explanation in either light novel or manga format. However, it appears that station is based on one's power and abilities. Vampires turned by the first progenitor are the strongest, so they fill up the first ranks. Saito (a 2nd) sired Ferid, who is a 7th progenitor, roughly 5 ranks back. Someone sired by Ferid would be estimated to be a 13th progenitor, which is why Crowley fakes being that rank. This is about 6 ranks back.

I suspect those estimates may just be based on the power of a noble. This would mean that those places may be filled in at some point. There are only 2 2nd progenitors, 3 3rd progenitors, 4 4th progenitors, and so on. This is confirmed. With progenitor deaths, it makes sense that lower-ranking vampires could move up the ranks. Characters like Mika, Lacus, or Rene could even acquire nobility and become progenitors themselves if this theory is correct. The simplest solution to determine power would be a straight-forward battle, but we have no information on how they determine these things. All we know is that progenitors with lower numbers are ranked highest in power.

With that in mind, the 1st progenitor and Saito, a 2nd progenitor, disappeared some time ago, and those spots have not been filled.

So basically we have no clue but a few theories!