While twins normally share everything, these twins won't be sharing the same birthday after they were born in different years.
The de Jesus Ontiveros twins weren't due until January 27 but instead made an early entrance - one in 2017 and one in 2018.
At 7pm on New Year's Eve, their mother Maria went into labour prematurely and the babies arrived naturally either side of midnight in California's Delano Regional Medical Centre in the US.
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, Turnto23 reports.
It means the duo won't share the same birth year, birth month or even birthday.
Their birth dates are incredibly uncommon, but 12 months ago four such twin births were recorded in the US - in Georgia, Utah, Arizona and San Diego in California.
The year before, there was just one, also in San Diego.