Many times, the role of a Wedding Planner is also "Counselor, Babysitter, good Listener, Peace-Keeper."
I can't begin to tell you the number of times that I have had to come between family members, call off fights, listen to sob stories, etc.
For the most part, I really don't mind and know that it goes with the job, but there are some times when you really need to understand that your private life should be kept private and not aired in public.
For instance; your guests really don't need to know that you can't stand your brother's college buddy. Just be a gracious host and not throw a drink in his face and the first body slam when he tried to hug the bride.
Try not to yell at the busboy in front of your 175 guests because he dropped a fork on the floor when he has 10 plates in his hands because you demanded he take "just one more."
If your cousin twice removed shows up to your reception, please don't yell into the microphone about his drunken escapades at your house last Christmas. Be a gracious host and ask him quietly and privately to leave or you will need to call security. I have had to do this numerous times and not one guest ever knew of the situation.
Most issues at any event can be taken care of privately and discreetly and in complete control of the situation, not shamelessly hauled out for public viewing.
At a wedding, everyone is equal, so if you have an issue with your father's new wife, your brother's weird girlfriend, or your cousin with the red and orange hair, either be a gracious and polite host and welcome them with a smile and a handshake or don't invite them in the first place. You can rant and rave the next day--today is your wedding day!