DEAR MISS MANNERS: My boyfriend and I have just started planning our wedding and asking our dearest friends to participate. Is it inappropriate to include his cousin in the wedding party but exclude his sister? What does Miss Manners care which of them writes as long as the letters get written? In forming a wedding party, it is ridiculous to feel that gender is more important than the relationship. (Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Andrews McMeel Syndication, 1130 Walnut St., Kansas City, MO 64106.)