Cheesepie (top left) is the daughter cheese pie and pinkie pie had before they started dating skystar, she takes after her father in her love of cheese based foods, and is known for making cheese versions of and mixing cheese with the craziest foods.  
Pecan Pie (top right) was born next, she’s timid and quiet, like her aunt Maud, but pinkie loves her and understands her. She loves her aunt and took on her love of rocks, but mostly the art of rocks instead of the science. She’s a sculptor, and she sculpts with her beak.  
Tuna Pie (bottom left) was born next, taking on some of her mom’s aquatic genes, and the only one who didn’t pick up the pony gene of cutie marks. At least as far as she knows. She loves to swim, and is pretty antisocial.  
Mud Pie (bottom right) was born last. He took on music, like his mother pinkie pie, very early on and it’s been his passion ever since. He got his cutie mark really fast because of that. He’s a fun and chill dude.