Phil and Penny

I felt that they did love another, but expressed their love in ways that the other didn't appreciate. Penny expresses it by her work -- the cooking, cleaning, and so on -- that the all the family enjoy, and she expects others to work in the same way. When they do, that's when she feels love. When Phil doesn't get up early and take his work seriously though, she doesn't feel it.

Phil, on the other hand, looks for words of support. He needs to hear that he is loved and appreciated, and when he doesn't hear that he loses hope. When he hears nagging -- which is the opposite -- he moves toward despair.

I hope the two have finally learned that about one another by the film's end.