So in the "Cayde's Stash" mission, you can go into a secret room that Cayde had, and there's some cool dialogue.
He says that the hearts in his deck of cards stood for a girl he loved. When pressed about it, he uncomfortably avoids the question.
Could the girl have been The Stranger? I think either that or maybe Amanda Holliday. But probably The Stranger.
-
What I think happened: Cayde was a person once,mind got put into exo. He loved Dr. Maya Sundaresh,but she was killed by the vex. Her mind was most likely put into the stranger's exo,because that would explain why the stranger has so much hate for the Vex.