Custom Ponies

 

This is Smiley Apple. She is Applejack's daughter.

 This is Vanilla Ice.

This is Spring Breeze. She helps with the weather!

This is Lightning Dash. He is Rainbow Dash's brother.

This is Prince Red Hot. He is Princess Celestia's brother.

 This is Prince Red Hot when he was a colt.

 This is Lemonade. She is Applejack's aunt.

This is Night Light. She is Lightning Dash's sister.

This is Lemon Ice. He is Lemonade's husband.

This is Diamond Ice. He is Rarity's brother.

This Mint Ice Cream. He is Pinky Pie's older brother.

 This is Grandpa Sparkle. He is Twilight's Grandpa.

This is Ocean Blossom. She isn't related to anyone.

 This is Summer Sunshine. She is Rainbow Dash's Daughter.

 This is Heat Wave. He is Rainbow Dash's husband.

 This is Tropical Snow. He is Princess Celestia's nephew, and Rarity's Husband.

Custom Base Ponies

This is Cupcake Batter. She is Pinkie Pie's sister.

 This is Midnight Moon. She is Twilight's sister.

 This is Torch. He is Granny Smith's nephew.

 This is Fire Star. She is Torch's wife.

This is Dragonfly. She is Fluttershy's cousin.

 This is Rainbow and Dash. They are Rainbow Dash's parents.

  This is Rainbow and Rainbow Dash. Rainbow is Rainbow Dash's mother.

 This is Checker. He is Torch's son.

 This is White Saphire. She is Rainbow Dash's cousin.