User blog comment:Morganaforever/Are Arthur and Morgana siblings after all?/@comment-3012002-20120104231247

You do have a point but if you think about it, Nimueh only helped Ygraine concieve but making her able to concieve and then probably Uther did his bit. Remember, there wasn't anything wrong with Uther since he slept with Vivienne hence Morgana's conception. Think of it as a three-way conception.