In season 3 episode 8, when Babs comes for the family reunion, she talks about her new school, then apple bloom asks if she has met any other blankflanks there, and then Babs replies, "Yes, two." I am guessing those two are star dreams and another pegasus filly I have no idea who he/she is. Let's discuss some more ideas about Babs' branch now shall we?
Star Dreams?
And yes, they probably follow the earth pony + pegasus + unicorn thinger.
We have Babs,
(http://doubleaardvarkmedia.com/wp-content/uploads/2012/11/babs_seed_vector_by_marelynmanson-d5lryqw-450-x-559.jpg)
Star Dreams,
(http://oi39.tinypic.com/6fz7mu.jpg)
and now we need a pegasus to complete Babs seed's CMC branch.
(http://oi42.tinypic.com/wujjpe.jpg)
Who do you think it will be?