Yes, your wedding is your day, and you have the right to choose whatever makes you happy on your special day, BUT I don't believe not inviting your sister and her husband would truly make you happy on the day. Plus, it could create a rift between yourself and your family that could take many years to heal. As has been suggested by woofgang, maybe you could talk to your sister, tell her you love her and want your family at your wedding, but ask her (politely) to keep her mouth shut for one day, and smile. Alternatively, if you can't talk to her like this, invite her anyway and just set your mind on having a completely fabulous day, that nobody can spoil. Then you can settle into married life knowing that you were the bigger person, and your happiness will speak for itself.