I personally saw nothing distasteful with mentioning his grandpa, given this had happened over a month ago. Again, provided JT didn’t ask him to not go there prior to the interview.
At what point is it "okay" to bring that up if a month is too soon?
Not really worth debating, but I just personally felt that it wasn’t out of bounds. JT even chuckled a bit when he said, "“you had to go there didn’t you."
Had his demeanor been more serious, perhaps I’d agree.