User blog comment:Mnzombie/Issei's Peerage/@comment-139.168.116.203-20131206051903/@comment-1359322-20131206100538

Well if we see Rias and Akeno's encounter story, Rias didn't received hers till she entered Junior High. Well based on this:


 * And around the time when Rias entered junior high, she received her evil pieces from her father.

Maybe the Devil receives the Evil Pieces from the parents? Well it also seems like Ravel became Riser's Bishop earlier than her required age to become a King thus she lost her rights as King.