I will give you a brief description of the minor characters of this excellent play as I see them. I have also included links to the enotes study section so that you can investigate them in more depth if you want. Hope this helps! Ferdinand: Ferdinand is the son and heir of Alonso, and becomes romantically involved with Miranda on the island. He is similar to Miranda because of his innocence and purity. He submits to servitude so that he can win Prospero's blessing and approval. Alonso: Alonso is the King of Naples and he helped Antonio in exiling Prospero prior to the play. However, when he appears in the play, he displays considerable guilt for his actions and comes to recognise his own wrongdoings in relation to Prosper. Antonio: Antonio is a power-hungry and rather intellectually limited character. He is Prospero's brother, and bullies Sebastian into trying to kill Alonso while he is sleeping. His story of fending off lions when Gonzalo wakes up and sees them indicates his violence and his stupidity. Sebastian: Sebastian is the brother of Alonso, and is similar to Antonio in that he is violent but also cowardly when faced with opposition.
Gonzalo: Gonzalo was the honest lord that aided Prospero and Miranda when they were exiled so long ago. He stands in contrast with characters such as Sebastian and Antonio. Trinculo and Stephano: These two characters are, respectively, a jester and a drunken butler, who provide a comic foil to the more serious pairings of characters. Their squabbles over power their drunken antics serve to contrast the machinations of the characters of the main plot. Boatswain: The boatswain appears only in the first and last scenes of the play, and again, is placed in contrast with the more noble characters that surround him. He is immensely capable and is shown to be surprised when he wakes from his enchanted sleep at the end of the play.