This story is like a fable, a story usually (but not always) with animals as characters, which teaches some moral lesson. There are a few themes in this story, all centered around love: generosity, family, giving, selflessness. In this story, Rob realizes that his father (and mother) love him when he overhears his father lamenting the fact that he has to wake his son every morning to help with the farm work. Rob had always done so reluctantly. But upon overhearing this conversation, Rob discovers that his parents had simply been too busy with work to tell him how they loved him. With this epiphany, Rob becomes selfless, decides to be more helpful, to reciprocate love.
One of the other lessons and/or themes of the story is the reciprocal nature of love, the chain reaction it can create. As soon as Rob knows he is loved, he becomes a more loving son. And he takes that new attitude with him for the rest of his life. He learns that love begets love.