[kateee]

I am a member of a relatively new family line. My big big was part of a HUGE 'family', the turtle family, and she herself had four littles and like six grandlittles. So since the turtle family was so large, my big big chose to branch off into the peacock family. It wasn't a matter of not liking her own family anymore, it was because said family was so large that it was basically the entire chapter (our ceiling is set at 35 girls.) Since then, the turtle family has almost died off, leaving one member before big/little this year. We joked that we were all becoming turtles to keep them going! :P
In this instance, at the time branching off into a new family line seemed like a great idea at a time. The turtle family was waaayyy to big, and big big had a large enough branch to form her own family. However, in retrospect, this year we almost rejoined the turtle family because they were too small.
I don't think there is really any reason to start a new family line unless yours is just way too big. *shrugs* Just speaking from a semi-personal experience here.