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