That would be more likely to happen if they were both under the same Management or Record Label, which they're not. Plus, they probably don't want to do the "sisters" thing. It's kinda lame as a gimmick. I mean, look at *shudders violently* Ashlee and Jessica Simpson or Beyonce and Solange Knowles. Sisters in the music biz, but they don't go out of their way to promote that fact. Each wants to do her own thing, and be recognized for THAT, not for the fact that they're related.