With big shots, it all depends, are these cousins, with a small c or Cousins with a capital C or COUSINS, all caps, which probabably means their mother and father are sister and brother to your father and mother.
Small c, you are free to insult or ignore- the only heat you'll get is from them, and that is only if they actually register your existence. People like that usually don't know other people breathe. Everyone else will understand.
Capital C means you have to see them every week at the barbecue, the only way you can avoid them is not going, but that's cutting off your nose to spite your face. Short of open warfare, which is sometimes called for, but not for this penny ante stuff, you can take measures. Under no circumstances try to do them one better, you can't. Instead confine yourself to this one comment, every time. : You are the luckiest, smartest, bravest, thriftiest- pick whatever adjective applies to the circumstance- people I have ever heard of. Madonna, I hope you are wearing a little red ribbon. Trust me, after a while they will stop. But you have to say it like you mean it. This will make them nervous.
ALL CAPITALS- You are stuck with these people, no matter what. The only way you can break from them is amputation. If they're gangrene, by any means, you cut them out of your life. Just be sure it's an arm or a leg your cutting out, not a heart or a liver. God bless, Donna