Here's Pinkie Pie's family. Pinkie Pie is married to Cheese Sandwich and they have two children.
Both are girls, older Sugar Spice and younger Lil Cheese.
Here comes information about them.

Name: Sugar Spice
Age: 23 years old
Place of birth and current location: Ponyville
Parents: Pinkie Pie (mother) and Cheese Sandwich (father)
Siblings: little sister Lil Cheese
Species: Earth pony
Gender Woman
Cutie Mark: Three muffins. Got it when you succeeded in baking a wonderful cake.
Crush:Apple Road
More information:
Sugar Spice loves to bake and has taught her little sister. She also loves parties, but not in the same way as her mother Pinkie.
Dreams of owning a bakery with Pear Cupcake in the future.
Now still working at Sugarcube Corner.

Name: Lil Cheese
Age: 12 years old
Place of birth and current location: Ponyville
Parents: Pinkie Pie (mother) and Cheese Sandwich (father)
Siblings: older sister Sugar Spice
Species: Earth pony
Gender Woman
Cutie mark: a slice of cheesecake. Got it when he learned to bake with his sister and got excited about it.
More information:
Lil Cheese is a school age Earth pony filly. She gets excited really quickly and is always going somewhere.
Her best friend is Apple Sunlight.

Lil Cheese, Pinkie Pie, Cheese Sandwich and Sugar Spice