Sometimes, planning a party is a delicate affair, especially when family members are involved. If you leave out unwanted family members when you send the invitations, chances are they are going to hear about it from someone else. And then, depending on your family dynamics, drama will ensue. It can help to examine why the family member isn't welcome and pick your battles carefully. If the family member has caused harm to you or your family, it's always okay to exclude the person.
Keep It Simple
It's generally considered impolite to leave one family member out of an invitation and invite another unless you can really simplify the guest list. One of the best ways to exclude certain family members without creating drama is to keep the party very small. Instead of throwing a big birthday bash, throw a small "grandparents only" party. To avoid hurt feelings, let other family members know that you feel like too many guests will overwhelm your young child, or that you simply don't have the time to throw a large family bash this year.
Keep To A Theme
If you do want to have a large family gathering, etiquette states that you may have to invite that unwanted family member. But, that doesn't mean you can't gently discourage them from attending. Try moving the party to a location where the other family member may not be able to or want to attend, such as a women's only gathering at a day spa or a day at the ballpark. This is no guarantee that the unwanted family member won't come, however, which you will need to take into account.
Keep Guests Busy
If you do have to invite that unwanted family member to the party -- and in some situations, it just might have to happen, especially if the family member is a close relation -- try to think of a way to keep her busy and out of the way. It's not polite to send her a invitation that is conditional on her helping out at the party, so send her a formal invitation and then call her up and ask her if she's willing to help. For example, if the unwanted member is your mother-in-law, ask her if she will be the official photographer, as her photos are so gorgeous. Or, compliment her on her cooking, and then ask her if she'll spend some time in the kitchen whipping up her famous shrimp appetizers. If she prefers to attend as just a guest, ask another family member who gets along well with the unwanted person if he will run interference for you. Chances are, he may be able to head off an uncomfortable situation if the unwanted guest's behavior gets out of hand.
Keep It Honest
A brave way to handle the situation is to simply tell the truth. Maybe the unwanted family member tends to drink too much at parties, or doesn't get along with your husband. If the reason for excluding the family member is a valid one, honesty may indeed be the best policy to follow in this case. If you are lucky, it might pave the way for a discussion as to how the family member can get help for his problem, or how he can improve the relationship between himself and the rest of the family. It might be best to have a support system nearby -- perhaps other family members -- if you are going to confront the person.