Info on the Inquisitor's numerical designations...
From a Rebels press conference in October 2015 with Dave Filoni, Ashley Eckstein, Vanessa Marshall, Freddie Prinze, Jr., and Dee Bradley Baker:
"Since we know that Sarah Michelle Gellar is playing the Seventh Sister, a fan asked if there were six sisters prior to her. “I would say that that’s a logical conclusion. That’s an entirely logical thing to assume, that she’s the seventh–the latest version–so we’ll have to see what that means.”
http://thewookieegunner.com/2015/10...ope-interviews/
Seems to imply that there numbers refer to when they joined the organisation rather than rank within the organisation. And that there may only be one Sister and one Brother at any given time. These being the latest. Thoughts?