Will, his son
Did John know Will was his son the whole time he worked there? Was he working there on purpose to be close to him? It seemed like he didnt know until Will figured it out.
shareThat's a good question.
I'd thought at the end of the movie the surprise exhibited by John was merely due to Will overhearing the "Partee" conversation by mistake, but it would seem unlikely that John wouldn't have known who Will was after coming back to a place he'd lived a relatively short time from his past before, and especially after having worked with Will for ten years.
It also didn't take long at all for John to confirm Will's recollections about his father after realizing he'd overheard the conversation and slip right into the role of his father.
Your question makes me want to watch the scene again where Will is informally questioning John to determine his "sanity" to see if there are any father-son undertones being hinted at by John.