Colleague's attractive wife coming to office?

I am presently facing an extremely unfair occurrence at my workplace. Several colleagues, including myself, have been asking for a raise for the last year with no result, except for one guy. Not only is he making more money than others with more experience, proven track record etc, he just got a promotion and a new office. To make matters worst, a few weeks back I came across his wife in the corridor. She was with the boss and he was kissing her against the wall. Now I thought may be my colleague was not aware of this, but at another time I saw the boss holding her waist while the three of them were talking together. I also remember how the boss was dancing with her at the office party last year. Now I think the reason this guy is getting all the favors is because his wife who is very attractive is sleeping with the boss. I want to if this is a common occurrence at the workplace? Is so what am I supposed to do against this?