discuss the relationship between duke fredrick and duke senior

At the beginning of the play the reader is informed that Duke Senior, the rightful ruler, has been usurped by his brother, Duke Frederick, and banished to the woods....We are given a comparison between the evils represented within the new court and the timelessness of the Forest..... Duke Frederick, the usurper, continues his path of paranoia and wickedness when accusing his niece, Rosalind, of being her father's spy.....Rosalind is pitied by the people, and is a constant reminder of Frederick's actions against his beloved brother. She is banished from court.....He rightfully wants to lead without his “good” brother overshadowing him in his subject’s eyes.

The above excerpts are taken from a small article on Catharsis in Shakespeare's As You Like It. I will list it in the source link below.