How can family members refuse a wedding invitation?

Family, you've got to love 'em! On my side I get the "your going to hell Christmas cards" On my husbands side his bro is suing his dad!( How Sharper than a serpents tooth it is to have an ungrateful child) I believe that weddings are whatever the bride wants them to be. The family should go along(short of animal sacrifice, of course) some people can't take responsibility for themselves and so have to make up a reason not to be involved. How about saying they just don't want to come???