This is Flurry Heart with her besties, Pound cake and Pumpkin cake. Like I mentions a long time ago, I kind of theorize that since Pound and Pumpkin are only a few years older than Flurry, that whenever Cadence visited she would have Pinkie watch the three of them together. As such, they became friends and often hung out.
Pumpkin is the tougher of the twins, generally the one to take charge and responsibility when things go wrong (Which is often). Pound is a lot more calm and carefree (and often the reason things get bad to begin with.) Flurry is the drive of the group, always the one to suggest things to do and rushing off to do it.