Identical twins don't usually come with physical differences, but for two remarkable Texas twins, being mistaken for mother and daughter is a regular occurrence.
20-year-olds Sierra and Sienna Bernal are identical twin sisters but were born with a significant difference: Sienna has Primordial Dwarfism.
The condition causes small body size, resulting in Sienna being more than a foot smaller than Sierra, and weighing only 50 pounds, in comparison to Sierra's 98 pounds.
Sierra told Barcroft TV: "Sometimes whenever people find out we're twins they'll ask 'how old is she?' So a lot of times even after you've established that we're twins they'll ask Sienna if she's younger. I'm like 'that's how twins work, we're the exact same age'. And even sometimes people think she's my daughter."
See their incredible story in the video above.