CMCs

I made the Cutie Mark Crusaders in the universe of
Scootaloo is the oldest of them, and is old enough to foalsit them. She's Rainbow Dash's biological little sister, and she knows basic flying skills.
Apple Bloom is a cat like her sister.
Rarity adopted Sweetie Belle from an orphanage. She's the same age as Apple Bloom.
Twilight found Spike on her doorstep one day and no one knows where he came from or why he's an alicorn. Even though Spike's the youngest, he's the most responsible of the CMC.

Technically Apple Bloom is not a Cutie Mark Crusader, but she likes hanging out with her friends and doing the stunts they try.