As more states continue to legalize gay marriage, an issue for many gay couples is whether or not to invite friends and family who don't approve of their "lifestyle". The etiquette surrounding gay marriage is new, but some things are constant. Many heterosexual couples are also in relationships that aren't approved of by their friends and family, and have faced this issue. A good rule of thumb is for the couple to examine why they are inviting someone, how they would feel if they did not invite them, and if they are prepared for either response on the RSVP card.
Of course, almost everyone wants their parents at their wedding. If the couple decides to invite family to the wedding who have not been supportive of their relationship to this point, they need to be prepared to have their invitation declined. Ultimately, every couple with this decision must decide how much they would regret not sending the invitation and proceed from there.