User blog comment:Morganaforever/Are Arthur and Morgana siblings after all?/@comment-5036924-20120105204905/@comment-4650675-20120105212839

About Morgana, I do not have so many doubts, because Uther slept with Vivianne while her husband was away, maybe for more than enough months for the child to be considered his own and not Gorlois'. Uther sounded 100% positive when he expressed that Morgana is his daughter too. About Arthur, though...not so sure. He has no traits of Uther's personality within him, whereas Morgana has most of them. Maybe Nimueh, since she knew Arthur was destined to be the legendary king, (remember how she knew his time of dying had not come yet?) made it so that Uther wouldn't be required so that Arthur wouldn't take after him and also gifted Arthur with some traits that are necessary for a good king. After all, Morgana, who had a natural conception, was as bad a queen as Uther was for a king. Also, Morgana's reaction towards Arthur and vice versa seem to make perfect sense this way. For example, one can understand this way why Morgana thinks she is the only rightful heir to the throne. She' a woman and possibly she's also younger, so the only way for her rights to be acceptable would be if Arthur is not Uther's child. Maybe that's why Morgana's so sarcastic when she calls him "dear brother" and Arthur does not call her sister at all, but "my lady", as he used to back in season 1.