One who is in the process of application to become a Night-Child in Notte’s family. Only humans can be turned into vampires, and the human has to pass a series of tests and take a number of classes both before and after turning.
Notte is pretty darned picky about who’s allowed to be turned.
As an aside, Ravena takes whomever she darned well pleases, but she has to keep them under the radar.