Who are the six major characters in Othello, and what is their relationship at the beginning of the play?

The six major characters are:

Othello - Moorish general beloved by the royalty of Venice until he woos Desdemona, Brabantio(a nobleman)'s daughter when some of them turn against him.

Iago - Othello's loyal right hand man (on the surface) and his worst enemy underneath.  Angry at being passed over for promotion, a genius at manipulation

Desdemona - Othello's girlfriend then wife, completely and totally devoted to Othello

Cassio - Othello's lieutenant, promoted over Iago, darling of the Venetians as he is of noble birth

Roderigo - Iago's stooge, wants to be with Desdemona but can't pull it off, funds much of Iago's plans

Emilia - Iago's wife, knows her husband and is the first to see through all the plots