Twins Or Sisters

Riddle: Two girls have the same parent's, they were born in the same hour of the same day of the same month. But they are not twins, how can thus be possible?

Answer: They were born in different years. Source: https://riddles.com/9166

Two girls have the same parent's, they were born in the same hour of the same day of the same month. But they are not twins, how can thus be possible? — Twins or sisters by Dangerous Cougars Riddle