Does the embassy offer certification?

Hi, my parents bothy have chinese lastnames and they were born here, my grandfather is pure chinese, he had his oathtaking years ago and now we are all planning to got to china to see visit but due to my work i was not permitted to go unless we have a valid documentation aside from the passport that we have?, is there a way that the embassy could provide us a certification or a proof that will allow us to go? We have all the necessary documentations. Is it possible? Thanks and have a great day!:)