The twin babies born in two different years.

Well, this is going to complicate things.

That staple shutdown in sibling arguments ‘Well, I’m the eldest takes on a whole new meaning when an entire year separates you, even though you shared a womb and were born only 18 minutes apart.

Yep, the Ontiveros twins, who were born on New Year’s Eve in the US, won’t share the same birth date nor the same birth year.

The pair weren’t due until January 27, Yahoo Seven reports, but mum Maria Flores went into labour at 7pm on New Year’s Eve and attended California’s Delano Regional Medical Centre in Kern County for the births.

A little boy, Joaquin Jr. Ontiveros, arrived at 11.58pm on December 31, 2017 and his sister, Aitana de Jesus Ontiveros, was born at 12.16am on January 1, 2018.

“I’ve been in the practice for almost 30 plus years. I’ve never had the opportunity to do anything like that before,” delivering doctor, Seyed Tamjidi, told Kern Golden Empire.

There were added benefits to spending New Year’s Eve in labour, with Flores and her family reportedly gifted more than $3000 worth of baby gear by the hospital.

Aitana was also the first baby born in the county in 2018, Turnto23 reports.

What a way to leave 2017 with a bang and welcome the new year with something equally special. Congratulations!