Jaelyn Valencia was born at 11:59 p.m. Thursday, New Year's Eve, in Mission Valley at San Diego Kaiser Permanente Zion Medical Center. Her little brother, Luis, arrived at 12:02 a.m. Friday, New Year's Day.
The twins were born to mother Maribel, 22, and her husband, Luis Valencia, a couple from National City.
Jaelyn weighed four pounds, 15 ounces. Luis tipped the scales at five pounds, nine ounces.
Both infants were happy and healthy as was their mother following her delivery, a Kaiser spokeswoman said.
Maribel works as a cashier at San Diego International Airport, while husband Luis is a Navy diesel mechanic. The couple have another daughter, three-year-old Isabella.
Luis told FOX 5 the babies weren't expected for another month. In fact, the couple had plans to ring in the new year in Los Angeles. But the couple was excited when they found out about the possibility their little ones would come sooner.
"It's pretty much the best of both worlds," Luis said. "So that means two birthday parties back-to-back!"