Wendy Torrance: Stay away from me.
Jack Torrance: Why?
Wendy Torrance: I just wanna go back to my room.
Jack Torrance: Why?
Wendy Torrance: Well, I'm very confused and I just need time to think things over.
Jack Torrance: You've had your whole fucking life to think things over.
What good's a few minutes more gonna do you now?
Dick Halloran: They turned out to be completely unreliable assholes.
Jack Torrance: Little pigs. Little pigs. Let me come in. Now by the hair on your chinny chinny chin? Then, I'll huff, and I'll puff, and I'll blow your house in!
Jack Torrance: Here's Johnny!
Answer: Delbert Grady has always been at the hotel, just as Jack Torrance has...however, "Charles Grady" was one incarnation of the hotel's "caretaker", which Jack Torrance currently is. Delbert, evidenced by his appearance, occupation, and archaic racial views, has been with the hotel since its turn-of-the-century inception, just as Jack, in the photo at the end, has been. We don't know what "spirit-Jack's" function in the Overlook is...we only know that the present Jack (whom Delbert is talking to) embodies the "caretaker" who has always been there, just as Charles Grady did in his time. Delbert refers to his wife and two daughters, whom he did not murder...his "caretaker" version, Charles Grady, did that.