Not Twins

Riddle: Two girls have the same parents and were born at the same hour of the same day of the same month, but they are not twins. How can this be possible?

Answer: They were not born in the same year.

Source: https://www.riddles.com/108

Riddle: Two girls have the same parents and were born at the same hour of the same day of the same month, but they are not twins. How can this be possible? Answer: They were not born in the same year. — by Anonymous v1.

Riddle: Two girls have the same parents and were born at the same hour of the same day of the same month, but they are not twins. How can this be possible? Answer: They were not born in the same year. — by Anonymous v2.