It's hard to believe that two different size girls can actually be twins. Sienna Bernal is so small she can even hide behind her sister Sierra.
The girl's mother, Chrissy told INSIDE EDITION, "A primordial dwarf is a smaller, proportionate person, so it's almost like Honey, I Shrunk the Kids."
When their mom was pregnant, doctors didn't realize she was carrying twins until her sixth month because Sienna was so tiny.
"They said had they found her earlier they would have encouraged me to do selective reduction, in other words, abort Sienna and I said 'No, I'm glad you didn't find them,' " said Chrissy.
The twins were born three months prematurely. Sienna was only 12" long and weighed just over a pound.
Chrissy said, "She was so tiny, she was like a beanie baby."
Doctors gave Sienna a 10% chance of survival and against all odds she made it.
Now Sienna is a typical teenager and enjoys playing the drums. She helps her mom write a series of books about her challenges. Their latest book is Sienna's Locket. They hope the books shed light on the difficulties the little girl faces.
Sienna will always remain small but she accepts her fate with humor and is an inspiration to the rest of us as the tiny twin who lives life large every day.