Yes, this is a popular question. Below, I have provided a link to another answer, specifically referencing the brothers in Act One.
An important point to remember, when comparing Orlando and Oliver is that not only do they function in relationship to each other as individual characters, they provide continuity between the main plot and a subplot of the play -- the banishment of Duke Senior by his brother Duke Frederick. These four characters are, not coincidentally, two sets of brothers -- one brother is good and virtuous, one brother is devious and self-serving.
So, while the events of the main plot involving the romantic relationship between Rosalind and Orlando is influenced by the relationship between Orlando and Oliver, they also serve to connect this romantic main plot to the subplot of Duke Senior and Duke Frederick.
All four brothers also serve to highlight a more general theme in the play: the rustic and pure life of the pastoral setting of The Forest of Arden as contrasted with the scheming and corrupt world of the court. Oliver and Duke Frederick, of course, represent the brothers of the court world and Orlando and Duke Senior the brothers of the pastoral world.
So, while Orlando and Oliver certainly contrast against each other in personality, they also serve the larger structures of the play.
In the romantic pastoral comedy As You Like It by William Shakespeare, the characters of Orlando and Oliver are clearly distinguishable from each other.
Oliver is Orlando's elder brother. Both are the sons of late Sir Rowland de Bois. Right from the beginning, we find out that, in accordance with the rule of primogeniture in England, which instructs that all the property would be inherited by the eldest of the family, Orlando gets the possession of the belongings that his father leaves. Though, he was instructed to take proper care of Orlando, he, out of jealousy and loath, makes Orlando totally deprived, moreover "openly demonstrates his hostility toward Orlando by treating him like a servant and striking him when he criticizes Oliver's behaviour". In Act i, Scene i, the fact is obvious when Orlando expresses his grief while talking to Adam: "He lets me feed with his hinds..., mines my gentility with my education".
In fact, when the royal wrestler Charles is supposed to fight Orlando, Oliver leaps with joy thinking of the probable death of his brother. But, in Orlando, we find no such cruel feeling or motive. He is not even confident enough to stand on his own feet: "I know no wise remedy how to avoid it". He just flees away in fear of his brother.
Besides, Oliver scornfully addresses his old, trustworthy servant, Adam as "dog", whereas Orlando behaves with Adam very cordially. Though, being an educated and well-nurtured man, Oliver proves to be an uncouth person; while Orlando appears to be a well-behaved human being ill-nurtured.
In As You Like It, the primary focus is upon Orlando always. The playwright has delineated wonderfully the gradual developmentf of his personality. On the contrary, Oliver's character faces such a sudden, miraculous change, which is extremely hasty and unexpected, that this character does not get the chance to be highlighted enough.
Among these two brothers, Orlando becomes a favourite of all, while Oliver can gain a bit sympathy. They share hardly a little to be compared. Rather, they are more like mirror images.
The exposition of Shakespeare's "As You Like It" deals with the quarrel between the two sons of the late Sir Rowland de Boys. Through the means of this quarrel Shakespeare highlights the differences between the two brothers.
Oliver: is the elder brother and he has inherited his father's title and estate. Sir Rowland had mentioned in his will that he must look after his younger brother and give him a good education and bring him up like a gentleman. But Oliver out of jealousy denies his brother Orlando a gentleman's education and upbringing and treats him like an ordinary peasant worker on his estate. This clearly reveals that he is a jealous person.
Secondly, there is no reason for Oliver to be jealous of his younger brother Orlando and treat him in the unfair manner that he does. This clearly proves that he lacks self-confidence and is an insecure person.
Thirdly, this combination of jealousy and insecurity drives him to plan his younger brother's murder. He tells lies about Orlando to Duke Frederick's wrestler Charles and poisons his mind and tells him, "I had as lief thou didst break his neck as his finger." This clearly reveals to us his wicked and evil nature.
Orlando: the hero of the play, he is the younger brother of Oliver. The play opens with Orlando complaining righteously of the ill treatment meted out to him by his jealous and evil elder brother Oliver:
"for my part,
he keeps me rustically at home, or, to speak more
properly, stays me here at home unkept; for call you
that keeping for a gentleman of my birth, that
differs not from the stalling of an ox? His horses
are bred better; for, besides that they are fair
with their feeding, they are taught their manage,
and to that end riders dearly hired: but I, his
brother, gain nothing under him but growth; for the
which his animals on his dunghills are as much
bound to him as I. Besides this nothing that he so
plentifully gives me, the something that nature gave
me his countenance seems to take from me: he lets
me feed with his hinds, bars me the place of a
This clearly proves that he is 'an angry young man.'
Secondly Orlando is physically a very strong person. This can be seen from the fact that he is ready to challenge the strongest wrestler of his time namely, Charles.
Thirdly, perhaps most importantly, he is proud of his birth and lineage. When Oliver insults him by calling him a villain, he replies angrily:
I am no villain; I am the youngest son of Sir
Rowland de Boys; he was my father, and he is thrice
a villain that says such a father begot villains.
Wert thou not my brother, 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.
This clearly proves that he is "an angry young man."