User blog comment:B214/Talk About What You Want! 2/@comment-74.77.52.225-20140716184143/@comment-1359322-20140717160134

Yes and the King and Queen effects the other pieces. Of course Issei affected the others too, but not having a leader at that state is actually what cost the team to crumble fully. Issei is the center of the team while Rias leads the team with Akeno as the 2nd in command. During Volume 12, the Gremory team lost both its center and leader at the same time, so it was practically like the end of the team.