For those who don't understand the rank of an Aspirant:

An Aspirant is basically an intern so to speak or a pledge that wants to join a fraternity/sorority. A house finds interest in a human and tells them about the wonders of the ancient virus. The human then decides if he or she wants to become a vampire. If not, his mind is erased and it is like the meeting never happened. If yes, he must drop his life and enter the vampire nest. The aspirant will reside in a barrack or in a section in the main house designated for potential prospects. You swear secrecy and you begin serving the House - proving your character's worth. If you are able to help the prestige of the house or do something that the Elder can't turn away from, you will then be invited to the house (there's usually a ceremony). If you do not have anything to offer, they will erase your character's mind and he can go back to his old life. 

An aspirant usually has a vampire that supervises them (makes sure he/she does not reveal anything about the House). The vampire supervisor also double roles as their adviser. 

Other houses do not want another house to grow. That only means the house is getting stronger, so an aspirant may be the most endangered rank, since they are by the border of human and vampire.