User blog comment:Emily Windsnap/How old are the Merlin characters?/@comment-62.195.39.66-20200728183502

In season four the narration goes from 'Young boy' to 'Young man', meaning Merlin is 21 in season 4 since that's when they come off age, going off this Merlin's age would be:

16/17 - 17/18 - 19/20 - 21/22 - 24/25

Arthur would be 20/21 at the starts seeing as we see his coming off age ceremony in episode 9 or so which would mean for him:

20/21 - 21/22 - 24/25 - 26/27 - 29/30

Now I think Morgana might be older than Arthur by a year or so, but I'm not too sure, they're not too clear on that