Can my brother authenticate my bachelor certificate on my behalf ?

I am a Nigerian.I want to marry Chinese Girl,I am living in China now but I have finished the authentication of my Bachelorhood Certificate from Federal Ministry of Foreign affairs and the final stage is for China embassy to authenticate it but they refused to do it ,reason? that I should come in person.I gave my brother to help me do it he told me the answer he got was that they need to see my passport hard copy,I have sent photocopy but they didn't accept it Please advice.thanks