Shakespeare's Hamlet is a revenge play, but throughout the play we get a clear picture of the character of Hamlet as a man who sees his duty before him but who shirks it at every opportunity. Part of his dilemma is that he knows that the murder of his father was wrong, but he also realizes that vengeance is wrong.
There are 3 sets of fathers and sons in Hamlet: King Hamlet and Prince Hamlet, King Fortinbras and Prince Fortinbras, and Polonius and Laertes. Both Laetres and Prince Fortinbras serve as foils for Hamlet. That is, they provide a contrast to Hamlet and his character and behavior.