There are complicated ethics to this double-suicide (is it a murder-suicide, given how little clarity Grandma has?). But more than that, Grandpa’s willingness to die rather than be without his wife suggests that, unlike the narrator’s “defensive” thinking, Grandpa would rather take care of his loved ones than survive. This moment, too, is a lesson the narrator learns, though he never internalizes this “inheritance” as much as he does Dad’s harsher mentalities.