Oliver is the elder son of Sir Rowland de Boys and elder brother of Orlando. They have another brother, Jacques. Orlando is the youngest son and brother; Jacques is second born. Birth order is possibly the reason Oliver hates Orlando, for hate him he does. While Oliver sends Jacques to school to be educated as a gentleman, he ignores Orlando. Orlando, on the other hand, has borne with Oliver's neglect and done his best to make something of himself in his restricted circumstances; he has become a wrestler of great accomplishment.
Oliver has always acted in such a way as to provoke Orlando to wrath and, finally, on a day the play opens with, Orlando lets his wrath fly--this action is not without potentially disastrous consequences for Orlando.
ORLANDO: I would not take this hand
from thy throat till this other had pulled out thy
tongue for saying so: thou hast railed on thyself.
OLIVER: I will
physic your rankness, and yet give no thousand
Oliver stoops to unscrupulous and criminal means to get his will accomplished. Orlando seeks to "go buy [his] fortunes" through honest means, which is why he challenges the wrestling champion Charles in the competition. Oliver wishes to win in life through hatred and cheating. Orlando wishes to win through honesty and love.
ROSALIND: But, in good sooth, are you he
that hangs the verses on the trees, wherein Rosalind
is so admired?
Oliver is the villain with qualities antithetical to Orlando’s. Orlando is the hero whom Rosalind teases into maturity and eminence. Oliver is reformed when he falls in love with Celia. Orlando is improved through his love for Rosalind who leads him in the right path.
ROSALIND: I have promised to make all this matter even.
Keep you your word, O duke, to give your daughter;
You yours, Orlando, to receive his daughter: