User blog comment:Morganamagic7/Siblings Age/@comment-92.22.155.134-20120627213400

She was never 16. Arthur is 19 in the Dragon's Call (he turns 20 in later episodes of the same series) and Merlin is 17/18. Morgana is just a little older than Arthur (so she is about 20-22) and Morgause is even older than her, being about 25.

I read this information in an interview with producers.