中国大使馆网站说：需要Original and photocopy of certification (marriage certificate, birth certificate, certification of kinship issued by Public Security Bureau or notarized certification of kinship) showing the relationship of family members between applicant and inviting individual. 这个证明一定需要吗？打算让姐姐给我写邀请函，怎么提供证明邀请人是我亲姐姐呢？谢谢！