The back story on Jeff's father confirms that he was Gramps' son and that Gramps is Ellen's father-in-law.
Intimations of a back story for Jeff's father occur in this episode. Gramps alludes to "10 years ago" as if that is how long Jeff's father has been dead. The father's name is revealed to be John, as Gramps refers to him as "Johnny"; it's implied that he died during the war, most likely WWII, since the 10-year span of time would put the death during that war and the picture of him that Ellen sadly gazes at on the mantelpiece shows him in military uniform.