Theoretically the Brides parents are inviting everybody, although of course, nowadays it is quite often sorted out by the couple (as it was with us). So, the Brides parents don't get an invite (as they would be asking themselves), but they should invite the Grooms parents. The Bride and Groom don't get an invite, as it is assumed they will be there anyway!! Don't know the proper ettiquette for Bridesmaids/Best Man/Pages/Ushers, but we sent them an invite as usually you are asking the rest of their family as well.