User blog comment:OneofthePendragon94/The age of Merlin, Arthur, Morgana and Gwen./@comment-5674726-20121114162500

Arthur came of age during Series One, so he presumably turned twenty-one at the beginning of, or shortly before Excalibur. His birthday is likely to be in November or December, given that it happened after Samhain.

I'd say that Merlin is nineteen at the beginning of the series, given that he's likely to have been conceived shortly after Kilgharrah was captured.

I get the impression that Morgana and Arthur are very close in age, no more than a year or so apart. If that's the case, it seems more probable that she's slightly younger than slightly older, although the latter possibility can't be ruled out. Uther was very much in love with Ygraine and they must have been married at least several years before Arthur's birth, given that Uther was worried enough about their lack of an heir to seek magical help. Adultery seems unlikely. If it's a case of a grieving Uther and a lonely Vivienne having a one-night stand that resulted in a child, it would be another reason for Uther to be reluctant to acknowledge Morgana. I doubt that he'd want to admit to Arthur that he had an affair with another woman before Ygraine was cold.

I'd say that Guinevere is a few years older than you've suggested, given that she seems to have been Morgana's maid for at least a couple of years before the series began. It seems unlikely that a very young girl would be chosen for the job, since it'd be both demanding and an honoured position in the royal household. I'd have thought that Guinevere would be Morgana's age or possibly slightly older. In some ways, she strikes me as the oldest of the quartet, and while that could be partly because the actress is the oldest, I also think that the character has a more mature outlook than the others. However, that could be the result of her having to grow up fast, given that she lost her mother and was working.

All things considered, I'd say that there's no more than two or three years between the oldest and youngest of the quartet.