Rolfe
Adult human female
My own view, and I'm no expert, is that the swans represent ideals rather than carry a literal plot-line per se. Namely, the iconic battle between good and evil as symbolized by Odile as the black swan being evil and Odette in white representing good. All the more symbolic because they are both danced by the same person. And of course, good triumphs.
I wouldn't dispute any of that for a moment. This is a work of art with more than one layer to it. I'm only looking at a possible source for certain aspects of the basic plot - principally the hero Seigfried falling in love with the leader of the swan maidens (valkyries), then back in the real world being tricked into proposing to the wrong girl, with this oathbreaking eventually resulting in his death. (Siegfried does not commit suicide in Götterdämmerung, he is murdered as retribution for his apparent treachery, but Brünnhilde does subsequently commit suicide.)