Born twins, yet in two separate years

Mom and Lorraine (left)  and Brandon (right) 
                   (c) Washington Hospital Center

They are twins, born less than four minutes apart.  But amazingly they share different birthdays.  They were born in two separate days, two separate months and two separate years.  One was born in December, and the other in January.  One was born in 2013 and the other in 2014.
Do we still call them twins when one can claim to be older than the other by a year, after all she was born the year before her sibling was born.
That's the amazing story of Lorraine Yaleni Begazo and Brandon Ferdinando Begazo born in Washington D.C.  Lorraine was born December 31, 2013 at 11.58pm while Brandon was born January 1, 2014 at 12.01am.
The babies were born at MedStar Washington Hospital Center, in Washington, D.C. Lorraine weighed 6 pounds, 4.9 ounces, and Brandon was 5 pounds, 10.4 ounces.
"I feel wonderful, full of joy and happiness and a full sense of realization," said the twins' father, Warren Begazo, according to abcnews.com. "This is her first children ever, and they're beautiful and she's really happy."
"We really did celebrate New Year's Eve," Begazo said.