DRAMATIS PERSONAE
THE DUKE OF VENICE
THE PRINCE OF MOROCCO, suitor to Portia
THE PRINCE OF ARRAGON, suitor to Portia
ANTONIO, a merchant of Venice
THE DUKE OF VENICE  is a very minor character. He only appears in  Act 4, Scene 1  to serve as judge in the Antonio/Shylock trial. 
 (Although we all know Portia is the one really controlling that scene.)
The Merchant of Venice Characters of the Play