What docs required to apply for tourist visa?

My partner, myself and our 4 year old son plan to visit China in late October 2016 for 8 days only. I understand that we need to apply for L type. We are Malaysians. However we were told that we need to provide our son's birth certificate and also our marriage certificate to apply for a tourist one. Is this true? Why do they need a marriage certificate to apply for just a tourist type?