Doherty, once again, doesn't recommend acting unless you have significant clout: "The best man can be 6-foot-10 and 300 pounds — and when it comes to the dynamics in a family he's not part of, he's a wimp."
If you are part of the inner circle, you might say, "Let's settle down, everyone cool your jets, go to your separate corners. This is not what this event is about."
The good news: People generally seem to pull themselves together for major events and avoid the big conflagration that their relatives fear, Rubinowitz says.
"(And) if there's preplanning, you have a better chance of it working out."
Don't make it worse
There are plenty of things you can do to head off or defuse a big family fight … and a few approaches you probably shouldn't take:
Don't interfere if you don't have real influence over the key players. You could make matters worse.
Don't take sides. That just fuels the fire.
Don't get upset yourself. Your family needs a calm grown-up right now, not another overgrown child.
Source: William Doherty