Notarized Certificate of Relationship -

I am a Nepali HK resident and applying for family visit Visa to China. I am visiting my sister who works in China, the Consular in HK has requested proof of our relationship. My questions are:

1. Does the certificate of relationship have to be certified by the Chinese Embassy in Nepal or is a Nepali Notary sufficient?
2. Can the certificate of relationship be translated into English or does it have to be translated in Chinese?

Thanks very much.