Twins were born just 20 minutes apart - but in different years, months and days, Daily Mail reports.
Joaquin and Aitana de Jesus Ontiveros were both due to arrive January 27, 2018.
But at 7pm on New Year's Eve, their mother Maria went into labor prematurely, and the babies arrived naturally either side of midnight in California's Delano Regional Medical Center.
Joaquin, was born weighing 5lbs 9oz at 11.58pm on December 31, 2017, while his younger twin sister Aitana arrived at 12.16am on January 1, 2018, weighing 4lbs 10.8oz.
It means that while they share everything from genes to mealtimes, they will not share a birthday, birth month, or even a birth year.