If you have verbal siblings, give them a reading in the ceremony, let them announce the bridal party in your reception, or invite them to give a toast. If you have musical siblings, allow them to play or sing a solo of your choosing. If your siblings are not comfortable with public speaking, they can usher, oversee the guest book, or walk a family member down the aisle. Even designating them a privately planned yet publically seen element can be honoring, such as having them create a photo display, a floral arrangement, or a dessert that is prominately displayed with a by-line recognizing their handiwork.