I am. When my mother was pregnant with me, you took care of her, and we chose you to be my father because she was going to die.

[ He still doesn't like the idea of adopted but it is the correct word. And it does mean they chose one another rather than something like being biologically connected, the way he is with Lucifer. He wishes that Castiel was his father, truly. He would do anything for that to be the truth, and that he didn't have to worry all the time about what he was. Now that he has Lucifer's power literally running through his veins, it's an active fear. ]

But you were killed when I was born, so Sam and Dean took me in. But I helped bring you out of the Empty, so we could be together. You've all raised me the past three years.