Arthur Pendragon (Morgana)

Arthur Pendragon of Camelot is the son of Uther Pendragon and Igraine, brother of Anna Pendragon and maternal half brother of Morgana le Fay and Morgause. According to the White Dragon, Arthur is destined to be the enemy of Morgana.

Season 1
The White Dragon warned Morgana that Arthur would be her enemy.