Both Connie and Lonnie look similar to Bonnie, but are taller in height and have different hair colors than her--Lonnie has the same eye color and skin tone as Bonnie while Connie has paler skin than both of her sisters and has blue eyes rather than blue-green eyes. Connie has brown hair like Bonnie does, but her hair is much wavier and is also a lighter shade of brown--Lonnie's the only one of the three sisters to have a mole (just below her right eye) and the only one to have blonde hair, though it's unknown if she's a natural blonde or a bottle-blonde (meaning that she dyed her hair blonde). Lonnie's also considered to be the most beautiful of the Rockwaller-sisters.
Connie and Lonnie are basically just meaner versions of Bonnie, and it's implied in Bonding that Bonnie's mean-spirited demeanor is because of Connie and Lonnie's treatment towards her, as they're shown to be just as mean (if not meaner) to Bonnie as Bonnie typically is to others. Connie and Lonnie also aren't just mean/rude/snobby to their sister, but to others as well, such as Kim when she tried introducing herself to them.
Connie and Lonnie like to claim that the former "got all the brains," the latter "got all the looks" and that Bonnie "got the rest."
Not much is known about Connie and Lonnie's abilities, other than the fact that Connie's considered to be the most intelligent of the three sisters. However, considering that Bonnie claimed in Hidden Talent that her "older sibs" won the Middleton High School-talent show multiple years in a row when they were students at the school, they must have some kind of talents/abilities.
Role in the Series
Connie and Lonnie were first alluded in Hidden Talent, when Bonnie mentioned having "older sibs" who the MHS-talent show multiple years in a row when they were in high school, but didn't make any physical appearances until Bonding, when they came into Bonnie's room while she and Kim were getting ready to leave on a mission (Kim and Bonnie were literally joined at the hip at the time, so Kim was forced to bring Bonnie on the mission with her).
It's unknown what kind of relationship either Connie or Lonnie have with their mother--it's possible that she's just as embarrassing to them as she is to Bonnie.
Connie and Lonnie clearly aren't that close to Bonnie and greatly enjoy being mean to her.
Connie and Lonnie are clearly much closer to each other than they are to Bonnie (or possibly anyone else in their family), but it's unknown how often they hang out together, since they're ultimately only seen once in person (and aren't mentioned again after Bonding).