To have a homosexual affair in a dream (if you are straight) means you are admiring your own femininity or masculinity. Being proud of your gender. When men get a raise, land a client, score a hot date, etc. they may get a man on man dream because they did something particularly manly that day in real life. Women often get lesbian dreams when they are pregnant as that is the epitome of being female. Ask yourself what you have done that has been particularly manly or feminine lately.
To dream someone you know is gay, when in real life they are not, it suggests you feel they are not seeing or understanding both sides of an issue OR that they are too self-involved.