And nothing prevents a bride from appointing her brother as a bridesmaid or a groom from appointing his sister as a groomslady. While you may not need your bridesmaids or groomsmen to help you plan your wedding, there will be times when you will need to know you can rely on them. For example, if one of your bridesmaids is in charge of planning the wedding breakfast then it's important they have enough volunteers to cover for them if they don't show up. The most common appointment is for the brother or sister to serve as a witness to the marriage. If this is what you want to do then be sure to ask your pastor or priest whether this would be acceptable and appropriate. Sometimes other family members are invited to attend the wedding but not allowed to give testimony - for example, the father of the bride or groom might object if any relatives were allowed to serve as witnesses because they might feel excluded from some of the special moments during the ceremony. If you want to appoint someone else to act as a witness instead then this person should be able to testify as to what happened on the day without violating their privacy rights. For example, a best friend could serve as a witness if the couple wants to keep this information private until after the wedding. It's also acceptable for the brother-in-law or sister-in-law of the husband or wife to serve as a "giving witness" during their wedding reception.