In Pilot (2001), Cheyenne was 17, POSSIBLY close to her 18th birthday, and Kyra was 12, POSSIBLY just having a birthday. So now, 3 years and some months later, Cheyenne is turning 21 and Kyra SHOULD be at least 15, but in the last show, Happy Pills (2004), it's stated that she is still 14. Either Cheyenne is aging too fast or Kyra isn't aging fast enough.