In Act 2, Scene 3, Adam the servant informs Orlando of the plot his brother, Oliver, has hatched against his life. His language highlights the role that Oliver plays as a foil to Orlando:
Your brother—no, no brother—yet the son—
Yet not the son, I will not call him son—
Of him I was about to call his father,
Hath heard your praises, and this night he means
To burn the lodging where you use to lie,
And you within it.
Adam cannot bring himself to refer to Oliver as Orlando’s brother, nor as the son of their father. This is not only a mark of how much Adam dislikes Oliver, but also of how greatly Oliver’s character differs from that of his family. Adam cannot find grounds for comparison between the late, noble Sir Rowland de Boys, and Oliver, nor between kind Orlando and his brother. If any doubt about the dramatic difference between the latter two men exists, it is quickly obliterated with the reveal of Oliver’s plan: “...he means / to burn the lodging where you use to lie / and you within it.”
Orlando’s goodness brings Oliver’s selfishness into relief, and vice versa. What’s more, Orlando’s consistent generosity and morality also function as a meter stick against which to measure Oliver’s transformation over the course of the play. After Orlando saves Oliver’s life in the forest, the audience sees how the act of kindness affects Oliver so deeply that he begins to become more and more like his brother.
Like his brother, Oliver seeks reconciliation with his enemies; falls in love in an unselfish way; and detaches himself from the wealth and pomp of the court (as when he offers to give up his inheritance to marry Aliena). Orlando’s natural charity instigates this change in Oliver, who then longs to imitate it himself. One might argue that Adam is correct here, and that the action of the play is the long process of Oliver "becoming" Orlando's brother in more than name only.