Star Wars Qui-gon question?

In the first movie Yoda and the others didn't see Anakin becoming Darth Vader but Yoda did say that he had a bad feeling about him but he couldn't pinpoint what it was. Then in "Revenge of the Sith" after Anakin becomes Darth Vadar and Luke & Leia's mother dies after giving birth, Yoda tells Obi-Wan that Qui-gon's prophecy was not complete and that it would be Anakin's off spring (which was Luke & Leia) that would bring balance and piece to the rebellion.