Basically each family will have 3 parts before switching over to the next family. On holidays all the families will be together.
Families:
Fluttershy -Discord : Pandora
Rarity -Spike : Amethyst , Quartz
Big McIntosh - Sugar Belle : Apple Cobbler , Apple Crisp (twins)
Rainbow Dash-Soarin : Rain Cloud, Thunder Cloud (twins)
Twilight - Flash Sentry: Starry Sparkles
Pinkie- Cheese Sandwhich :Strawberry Swirl, Caramel Swirl

Cadence-Shining Armor : Flurry Heart (DUH)