Duke Frederick and Duke Senior are brothers, but they are as different as night and day. Duke Frederick, who is younger, is initially jealous of his brother Senior, and, when he somehow amasses enough power to do so, he banishes Duke Senior from the royal court, and plunders the estates of those who have accompanied him into exile. Duke Frederick's animosity towards his brother continues even after he has removed him from the court; when he learns of the influence Duke Senior still wields from the forest, his place of refuge, he sets out to eliminate him and his followers by force. Near the end of the story, however, Duke Frederick almost miraculously turns from his wicked ways when he is converted to a life of contemplation by a religious man in the Forest of Arden.
In contrast to Frederick, Duke Senior is a kind and virtuous man who draws others to himself because of his exemplary comportment. He is at one with nature, and is able to sustain himself off the land. Duke Senior lives simply, and as a ruler is much beloved. In his life in exile in the forest, he seems not to rule at all; he treats all men as equals, and his leadership is effective because of the strength of character he exudes. At the end of the story, when Duke Senior's kingdom is restored to him, the reader is left with the sense that all will be well because of his qualities of wisdom and benevolence.
The contrast between Duke senior & Duke Frederick is like earth & moon.Duke senior is virtuous man & attracts people towards himself whereas Duke Frederick is greedy & repels people. A man can recognized by the way he speaks.Here we see that Duke senior speaks kindly whereas Duke Frederick speaks unkindly&he scolds people of their mistakes though he already committed the mistake as in Act3,scene1 he calls Oliver a 'villain' for not loving Orlando but though he banished his own brother.We can get to know about Duke senior's virtues when he is accompanied by the lords in his banishment. Duke senior is a kind hearted person & helps people in whatever way he can Eg-when Orlando asks for food in Act2,scene7 he offers him food. Duke senior knows to see good in everything as he moralizes on the natural hardships faced by them in forest of Arden in Act2,scene1. Duke senior never forgets his friends and treats their offspring with same love. Duke Frederick is very humorous person.He kept Rosalind at the palace during her father's banishment but after-wards he banishes her too. Duke senior loves to debate with people as we know in Act2,scene2 where he says he would like to debate with Jacques. Duke senior has patience while Duke Frederick does not have patience & looses his control easily.