Ok Nate, I'm trying to think about the Father thing in, as Pip would say, "a crooked path".
My question is, does Ish's father know Ish exists?
So, I know Nate just answered this but I did the research today to prove it, and I can't let it go to waste. Ish's parents were married from March 3, 2325 to May 21, 2335, with Ish's birthday being August 1, 2333. So unless the circumstances were very unusual or Franklin Prescott Wang is not Ish's real father, neither of which seems to be the case from other dialog, then his father knows that Ish exists.
I think the real question is, does his father already know that Ish is in Diurnia?