Warning: To answer this riddle you need to have a thorough understanding of how time works.
Two twins were born during the same year, on the same month, and the same day, exactly 10 minutes apart. By the time twin A was 100, twin B was younger by more than 10 minutes, fairly slightly. Neither twin died during the 100 years.
How could Twin B be younger than Twin A by more than 10 minutes?