Sabe, a former Royal Handmaiden of Naboo, deduces from all the clues she’s gathered that feared Galactic Empire enforcer Darth Vader is actually the Jedi Anakin Skywalker, and father to Padme Amidala’s child. I say child since she only knows of Luke Skywalker and not of Leia Organa.
From – Star Wars: Darth Vader Vol. 1 #22 and 23